The authors thank the EPSRC and Intelligent Energy Ltd for funding this project. PB also thanks the SCI for the award of a Messel Scholarship.

数据记录软件1.建立<ol><li>安装数据采集和电子表格软件安装到配有RS232串行端口的计算机。 </li><li>将计算机连接到使用合适的RS232连接器电缆的平衡（在此方法中计算机和平衡需要9针连接器）。余额通常会被连接到COM1。 </li><li>打开数据采集软件。 </li><li>要记录数据在电子表格（ 如 Excel）中，去&#39;模式&#39;，然后&#39;发送键击"，在"应用程序标题栏文字"输入电子表格软件的适当的名称，然后选择"EXCEL.EXE"在在"命令行"，然后按"OK"。复选标记应该出现在旁边的"模式"下拉菜单"发送键击"。 </li><li>转到"端口"，然后"设置"，并确保这些值适合于有问题的平衡，然后按"OK";。 </li><li>转到&#39;定义&#39;，然后&#39;定义输入数据记录结构"，并选择"结束记录事件"部分的"收到的数字字符"中的"开始记录事件"部分和"回车或CRLF接收到的&#39;，然后按"继续"。 </li><li>当一个题为"输入记录结构"对话框出现时，选择"每个数据记录包含一个单独的数据字段"，然后按"继续"。 </li><li>当一箱名为"输入记录定义编辑器 - 发送键击模式"出现:在区域，设置"输入滤波器"到"数字数据只有"和"字段后记键击"到"{选项卡} {分钟} {二} {左} {} DOWN"，然后按"OK"。 </li><li>转到&#39;定义&#39;，然后&#39;定义热键和热的行动"。选择热键1，然后选择热键操作"暂停WinWedge&#39;和转让本的"退格"热键按键，然后按好。 </li><li>转到"文件"，然后"另存为"，然后保存方法在适当的文件夹。 </li></ol> 2.实验装置<ol><li>加水玻璃碗直到大约¾满。然后，放置在一个温度控制的搅拌器热板，并加热到50℃的玻璃碗;另外，使用恒温控制的水浴。 </li><li>添加去离子水（5毫升）的50ml圆底烧瓶中，并位置这在水浴使得水在浴水平远高于水在烧瓶中的水平。 </li><li>插入温度计入圆底烧瓶颈部监测水温（平衡后，水的烧瓶中的温度通常为〜5℃比在加热板设定点以下）。 注意:设置是准备就绪时将烧瓶内的水的温度保持在10分钟的时间常数。 </li><li>装满去离子水的烧杯中。 </li&gt; <li>将一个空烧杯到数据记录平衡。 </li><li>构造从塑料片可以从烧杯的喷口上的数据记录平衡转移水到空烧杯的桥梁。确保塑料桥不与在数据记录平衡烧杯物理接触。 </li><li>填的500毫升的量筒中，用去离子水。 </li><li>同时覆盖开口端用戴手套的手，反转量筒并放入烧杯中，使得所述测量圆筒的开口端仅仅是水的表面下。 </li><li>使用配有两个老板一个铁架台和夹具支持量筒。根据测量圆筒的大小，蒸馏的基础上发生的配重放置，以防止它由于掉落到水的重量。 </li><li>调整烧杯，使得喷口与所述塑料桥接触的位置。 </li><li>小心抬起量筒到llow的水和空气的进入释放以确保空气的测量圆筒中的水平是在每个实验开始时是一致的（例如100毫升的空气）。 </li><li>插入修饰的适配器的非磨口玻璃接头的一端插入管的长度。通过仔细地包装封口膜围绕接头和管道之间的连接密封。 </li><li>插入管导入量筒的末尾。 </li><li>确保在加入过量的水会导致其流失到平衡中加入一些水到烧杯中。泄漏可以在烧杯的开口和塑料桥之间的连接在高流速发生。 </li><li>确保余额不清零。如果有必要，加一些水，以对数据记录平衡烧杯中。 </li><li>用天平，称出或0.05，0.10，0.15，0.20，或0.25克硅放入小玻璃瓶中;一些硅趋向于被截留在其内不使用塑料称重舟将烧瓶颈部当从称量舟加入到反应混合物中。这个问题是由代替迅速反转一个小的玻璃瓶中放入烧瓶颈部避免。 </li></ol> 3.实验步骤<ol><li> （5毫升，20％重量）添加氢氧化钠溶液至50ml圆底烧瓶中，并位置这在水浴使得水在浴水平远高于水在烧瓶中的水平。 </li><li>插入温度计入圆底烧瓶颈部监测溶液的温度（平衡后，水的在此设置中，烧瓶中的温度通常为〜5℃比在加热板设定点以下）。 </li><li>离开10分钟以达到平衡。 </li><li>平衡期结束前，打开电子表格软件新的电子表格，然后打开数据收集软件。通过转到"文件"上的数据采集软件加载在步骤1中创建的方法开始菜单，然后"打开方式"。 </li><li>就在这10分钟的平衡期是由于结束，进入"激活"，然后点击"普通模式"。数据将开始在电子表格软件被记录。 </li><li>在10分钟的平衡周期结束时，通过迅速反转玻璃小瓶中，并在沉积所述硅进氢氧化钠溶液中添加硅。 </li><li>迅速放置其连接到管道成圆形的颈部适配器的磨口玻璃接头底烧瓶中。零平衡。在该天平归零的时刻将作为在数据分析时间（t）= 0。 </li><li> 10分钟过去了之后，按退格键，然后选择数据采集软件菜单上的"退出"选项停止对数据记录。保存在电子表格软件包中的文件。 </li><li>除去附着在管路从圆底烧瓶中的适配器并加水至阙NCH​​反应。 </li><li>通过离心或重力过滤分离在烧瓶中用于进一步分析的固体残余物​​中，或在整个反应混合物转移到烧杯中，并用盐酸（1 M）中和，并适当的废物处理。 </li></ol> 4.数据分析<ol><li>确保数据被加载到适当的电子表格软件包。 </li><li>寻找在天平归零的点;这被认为是（T）= 0点的反应。 </li><li>删除这之前该数据。 </li><li>插入一列到该数据的左侧。这将包含时间。 </li><li>添加适当的时间间隔，从0开始，向其中已插入的列。在这些研究中所用的平衡记录8.5个数据点每秒，并用于从而0.117647（= 1 / 8.5）秒的时间间隔。 </li><li>已收集的水考虑气体与水蒸汽饱和。在收集离子的过程中，测量圆筒中水位调整至保持在大气压力的测量圆筒中的内部压力。 </li><li>申请使用道尔顿定律，其中指出，在一个混合物中的气体（P 1 ... P N）的各个分压的总和等于总压力（P 合计 ）的近似校正因子。如，如果室内温度为298 K，水蒸汽的分压为31,69.9帕，并且测量圆筒中的气体的总压力为大气压（101325帕），它可以计算出有大约3.08％由所收集的气体中的体积的水蒸汽。通过使用水蒸汽的分压力在有关温度估计在其他温度下的氢的水蒸汽的量。 </li><li>以获得所产生的氢气的量的估计（如果室内温度是298K），乘以0.97的气体体积。 </li><li>估计最初的水力通过拟合线性趋势线的氢产生曲线的初始陡坡发电机产生率。 </li><li>取诱导期为采取对水的时间来从量筒位移。诱导期的这些估计都不是绝对的;实际氢产生反应在这些实验中估计为氢的一定量必须生成能够开始置换水的"诱导期"的结束前开始。然而，这些值允许在实验之间诱导期的相对的变化的评估。 </li></ol>

<ol>
	<li>Winter, M., Brodd, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=What+Are+Batteries,+Fuel+Cells,+and+Supercapacitors?.">What Are Batteries, Fuel Cells, and Supercapacitors?.</a> Chem. Rev. 104, 4245-4269 (2004).</li><li>Deng, Z. Y., Ferreira, J. M. F., Sakka, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen-generation+materials+for+portable+applications.">Hydrogen-generation materials for portable applications.</a> J. Am. Ceram. Soc. 91, 3825-3834 (2008).</li><li>Grew, K. N., Brownlee, Z. B., Shukla, K. C., Chu, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+Alane+as+a+hydrogen+storage+media+for+portable+fuel+cell+power+sources.">Assessment of Alane as a hydrogen storage media for portable fuel cell power sources.</a> J. Power Sources. 217, 417-430 (2012).</li><li>Fan, M. Q., Mei, D. S., Chen, D., Lv, C. J., Shu, K. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Portable+hydrogen+generation+from+activated+Al-Li-Bi+alloys+in+water.">Portable hydrogen generation from activated Al-Li-Bi alloys in water.</a> Renew. Energ. 36, 3061-3067 (2011).</li><li>Amendola, S. C., Sharp-goldman, S. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+safe,+portable,+hydrogen+gas+generator+using+aqueous+borohydride+solution+and+Ru+catalyst.">A safe, portable, hydrogen gas generator using aqueous borohydride solution and Ru catalyst.</a> Int. J. Hydrogen Energ. 25, 969-975 (2000).</li><li>Sharaf, O. Z., Orhan, M. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+overview+of+fuel+cell+technology:+Fundamentals+and+applications.">An overview of fuel cell technology: Fundamentals and applications.</a> Renew. Sust. Energ. Rev. 32, 810-853 (2014).</li><li>Wallace, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sodium+silicide+and+the+development+of+the+portable+hydrogen+energy+market.">Sodium silicide and the development of the portable hydrogen energy market.</a> ECS Trans. 42, 219-230 (2012).</li><li>Brack, P., Dann, S. E., Wijayantha, K. G. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heterogeneous+and+homogenous+catalysts+for+hydrogen+generation+by+hydrolysis+of+aqueous+sodium+borohydride+(NaBH4)+solutions.">Heterogeneous and homogenous catalysts for hydrogen generation by hydrolysis of aqueous sodium borohydride (NaBH4) solutions.</a> Energ. Sci. Eng. 3, 174-188 (2015).</li><li>Huang, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review:+Feasibility+of+hydrogen+generation+from+the+reaction+between+aluminum+and+water+for+fuel+cell+applications.">A review: Feasibility of hydrogen generation from the reaction between aluminum and water for fuel cell applications.</a> J. Power Sources. 229, 133-140 (2013).</li><li>McEvoy, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Joseph+Priestley.">Joseph Priestley.</a> Encyclopedia Britannica. , (2015).</li><li>The Editors of Encyclopædia Britannica. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stephen+Hales.">Stephen Hales.</a> Encyclopedia Britannica. , (2015).</li><li>Ai, L., Gao, X., Jiang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+synthesis+of+cobalt+stabilized+on+macroscopic+biopolymer+hydrogel+as+economical+and+recyclable+catalyst+for+hydrogen+generation+from+sodium+borohydride+hydrolysis.">In situ synthesis of cobalt stabilized on macroscopic biopolymer hydrogel as economical and recyclable catalyst for hydrogen generation from sodium borohydride hydrolysis.</a> J. Power Sources. 257, 213-220 (2014).</li><li>Chen, Y., Shi, Y., Liu, X., Zhang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+polyvinylidene+fluoride+-+nickel+hollow+fiber+catalytic+membranes+for+hydrogen+generation+from+sodium+borohydride.">Preparation of polyvinylidene fluoride - nickel hollow fiber catalytic membranes for hydrogen generation from sodium borohydride.</a> Fuel. 140, 685-692 (2015).</li><li>Demirci, S., Sahiner, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Superior+reusability+of+metal+catalysts+prepared+within+poly+(ethylene+imine)+microgels+for+H2+production+from+NaBH4+hydrolysis.">Superior reusability of metal catalysts prepared within poly (ethylene imine) microgels for H2 production from NaBH4 hydrolysis.</a> Fuel Process. Technol. 127, 88-96 (2014).</li><li>Loghmani, M. H., Shojaei, A. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen+production+through+hydrolysis+of+sodium+borohydride:+Oleic+acid+stabilized+Co-La-Zr-B+nanoparticle+as+a+novel+catalyst.">Hydrogen production through hydrolysis of sodium borohydride: Oleic acid stabilized Co-La-Zr-B nanoparticle as a novel catalyst.</a> Energy. 68, 152-159 (2014).</li><li>Manna, J., Roy, B., Vashistha, M., Sharma, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Co+2/BH-4+ratio+in+the+synthesis+of+Co-B+catalysts+on+sodium+borohydride+hydrolysis.">Effect of Co+2/BH-4 ratio in the synthesis of Co-B catalysts on sodium borohydride hydrolysis.</a> Int. J. Hydrogen Energ. 39, 406-413 (2014).</li><li>Saha, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Graphene+supported+bimetallic+G-Co-Pt+nanohybrid+catalyst+for+enhanced+and+cost+effective+hydrogen+generation.">Graphene supported bimetallic G-Co-Pt nanohybrid catalyst for enhanced and cost effective hydrogen generation.</a> Int. J. Hydrogen Energ. 39, 11566-11577 (2014).</li><li>Seven, F., Sahiner, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Superporous+P+(2-hydroxyethyl+methacrylate)+cryogel-M+(M+Co,+Ni,+Cu)+composites+as+highly+effective+catalysts+in+H2+generation+from+hydrolysis.">Superporous P (2-hydroxyethyl methacrylate) cryogel-M (M Co, Ni, Cu) composites as highly effective catalysts in H2 generation from hydrolysis.</a> Int. J. Hydrogen Energ. 39, 15455-15463 (2014).</li><li>Teprovich, J. A., Motyka, T., Zidan, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen+system+using+novel+additives+to+catalyze+hydrogen+release+from+the+hydrolysis+of+alane+and+activated+aluminum.">Hydrogen system using novel additives to catalyze hydrogen release from the hydrolysis of alane and activated aluminum.</a> Int. J. Hydrogen Energ. 37, 1594-1603 (2012).</li><li>Brack, P., Dann, S. E., Wijayantha, K. G. U., Adcock, P., Foster, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+old+solution+to+a+new+problem?+Hydrogen+generation+by+the+reaction+of+ferrosilicon+with+aqueous+sodium+hydroxide+solutions.">An old solution to a new problem? Hydrogen generation by the reaction of ferrosilicon with aqueous sodium hydroxide solutions.</a> Energ. Sci. Eng. 3, 535-540 (2015).</li><li>Akdim, O., Demirci, U. B., Miele, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+efficient+acid-treated+cobalt+catalyst+for+hydrogen+generation+from+NaBH4+hydrolysis.">Highly efficient acid-treated cobalt catalyst for hydrogen generation from NaBH4 hydrolysis.</a> Int. J. Hydrogen Energ. 34, 4780-4787 (2009).</li><li>Akdim, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anchored+cobalt+film+as+stable+supported+catalyst+for+hydrolysis+of+sodium+borohydride+for+chemical+hydrogen+storage.">Anchored cobalt film as stable supported catalyst for hydrolysis of sodium borohydride for chemical hydrogen storage.</a> Int. J. Hydrogen Energ. 36, 14527-14533 (2011).</li><li>Chamoun, R., Demirci, U. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cobalt-supported+alumina+as+catalytic+film+prepared+by+electrophoretic+deposition+for+hydrogen+release+applications.">Cobalt-supported alumina as catalytic film prepared by electrophoretic deposition for hydrogen release applications.</a> Appl. Surf. Sci. 256, 7684-7691 (2010).</li><li>Akdim, O., Demirci, U. B., Muller, D., Miele, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cobalt+(II)+salts,+performing+materials+for+generating+hydrogen+from+sodium+borohydride.">Cobalt (II) salts, performing materials for generating hydrogen from sodium borohydride.</a> Int. J. Hydrogen Energ. 34, 2631-2637 (2009).</li><li>Erogbogbo, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On-demand+hydrogen+generation+using+nanosilicon:+splitting+water+without+light,+heat,+or+electricity.">On-demand hydrogen generation using nanosilicon: splitting water without light, heat, or electricity.</a> Nano Lett. 13, 451-456 (2013).</li><li>Liu, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigation+on+the+improved+hydrolysis+of+aluminum-calcium+hydride-salt+mixture+elaborated+by+ball+milling.">Investigation on the improved hydrolysis of aluminum-calcium hydride-salt mixture elaborated by ball milling.</a> Energy. 84, 714-721 (2015).</li><li>Muir, S. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+electroless+plating+method+for+preparation+of+highly+active+Co-B+catalysts+for+NaBH4+hydrolysis.">New electroless plating method for preparation of highly active Co-B catalysts for NaBH4 hydrolysis.</a> Int. J. Hydrogen Energ. 39, 414-425 (2014).</li><li>Wu, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanism+and+kinetics+of+sodium+borohydride+hydrolysis+over+crystalline+nickel+and+nickel+boride+and+amorphous+nickel-boron+nanoparticles.">Mechanism and kinetics of sodium borohydride hydrolysis over crystalline nickel and nickel boride and amorphous nickel-boron nanoparticles.</a> J. Power Sources. 268, 596-603 (2014).</li><li>Zhuang, D. W., Zhang, J. J., Dai, H. B., Wang, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen+generation+from+hydrolysis+of+solid+sodium+borohydride+promoted+by+a+cobalt-molybdenum-boron+catalyst+and+aluminum+powder.">Hydrogen generation from hydrolysis of solid sodium borohydride promoted by a cobalt-molybdenum-boron catalyst and aluminum powder.</a> Int. J. Hydrogen Energ. 38, 10845-10850 (2013).</li><li>Chen, Y., Pan, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+various+Co-B+catalyst+synthesis+conditions+on+catalyst+surface+morphology+and+NaBH4+hydrolysis+reaction+kinetic+parameters.">Effect of various Co-B catalyst synthesis conditions on catalyst surface morphology and NaBH4 hydrolysis reaction kinetic parameters.</a> Int. J. Hydrogen Energ. 39, 1648-1663 (2014).</li><li>Cheng, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+active+nanoporous+Co-B-TiO2+framework+for+hydrolysis+of+NaBH4.">Highly active nanoporous Co-B-TiO2 framework for hydrolysis of NaBH4.</a> Ceram. Int. 41, 899-905 (2015).</li><li>Chinnappan, A., Kim, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanocatalyst:+Electrospun+nanofibers+of+PVDF+-+Dicationic+tetrachloronickelate+(II)+anion+and+their+effect+on+hydrogen+generation+from+the+hydrolysis+of+sodium+borohydride.">Nanocatalyst: Electrospun nanofibers of PVDF - Dicationic tetrachloronickelate (II) anion and their effect on hydrogen generation from the hydrolysis of sodium borohydride.</a> Int. J. Hydrogen Energ. 37, 18851-18859 (2012).</li><li>Shang, Y., Chen, R., Jiang, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetic+study+of+NaBH4+hydrolysis+over+carbon-supported+ruthenium.">Kinetic study of NaBH4 hydrolysis over carbon-supported ruthenium.</a> Int. J. Hydrogen Energ. 33, 6719-6726 (2008).</li><li>Shang, Y., Chen, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Semiempirical+Hydrogen+Generation+Model+Using+Concentrated+Sodium+Borohydride+Solution.">Semiempirical Hydrogen Generation Model Using Concentrated Sodium Borohydride Solution.</a> Energy Fuels. 20, 2149-2154 (2006).</li><li>Wang, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Promoted+Mo+incorporated+Co-Ru-B+catalyst+for+fast+hydrolysis+of+NaBH4+in+alkaline+solutions.">Promoted Mo incorporated Co-Ru-B catalyst for fast hydrolysis of NaBH4 in alkaline solutions.</a> Int. J. Hydrogen Energ. 39, 16202-16211 (2014).</li></ol>

The authors have nothing to disclose.

该协议的最重要的步骤是那些发生在一个实验的开始。这些水解反应的速率的大的温度依赖性意味着极大必须小心，以确保该溶液温度已在加入固体的前达到平衡。固体必须迅速并完全，适配器的磨口玻璃接头，必须正确插入圆底烧瓶的颈部，和余量然后必须尽可能迅速调零越好。的开始时间和反应温度的不正确的测量将产生不正确的结果。 该方法确实有一定的局限性。当务之急是插入量筒到其中的烧杯是尽可能的窄，以确保从量筒位移的水被迅速地引导向下塑料桥到平衡。否则，水的表面张力允许任意在低流速的水位的低积累（ 见图5），直到在该所有的水在一个大的滴被释放的点。 天平的误差也限制了数据的分辨率。在这些实验中，使用具有为±0.05克的错误的平衡，产生氢的数百毫升时，这是足够的，但如果正在测量较小体积具有较小误差的平衡将是需要的。 如从桥的位移水滴上的平衡，由天平记录质量产生振荡， 即 ，作为点滴落到平衡，平衡暂时记录一个稍大质量。这意味着使用的软件包高时间分辨率的原始数据的分化是有问题的梯度振荡。的最适当的方式找到氢产生曲线的最陡的部分的梯度，因此，氢生成速度，我s至适合的直线，并计算其梯度。 通过在电子表格自动登录的数据，该方法提供了精确度和时间分辨率相对于依赖于记录气体的手动放出的体积水置换方法显著改善。然而，虽然它在成本比它们使用相机和图像分析软件来跟踪气体放出方法相当低，这是在时间分辨率一般较低，并且这种基于相机的方法还避免了因水振荡质量平衡读数的问题形成液滴，因此，产生可以由分化更容易处理的数据。 水置换的方法是适用于在水中具有低溶解度的任何气体的集合。因此，该实验的协议可以被修改为从演进水溶性差的气体以外的化学反应产生气体的速率的测量上课。

由于它们的高能量密度，锂离子电池，目前最流行的电源为便携式消费电子之一。然而，可以由电池传递的能量的量是有限的。因此，存在目前正在制定提供便携式电源的替代方法的兴趣。一个更有前途的方法是利用质子交换膜（PEM）燃料电池，其通过组合氢和氧产生电和水。 PEM燃料电池有超过电池两大优点。首先，PEM燃料电池可以的时间长得多的周期提供电力（只要氢气流保持）。其次，这取决于燃料源上，PEM燃料电池可以具有比电池大得多的能量密度，这意味着一个较小的系统可以提供更多的能量。1,2-作为其结果，有一个目前定向的大量研究在开发可移植，按需氢源。2-7一种方法，它正在接收多的关注与水反应的化学物质是氢的生成。-8,9- 其中之一必须在这些反应进行测定的最重要的参数之一是氢的演变。对于简单的反应，例如氢气通过加入化学储氢材料以水溶液的演化，它有利的是具有一种简单的，低成本的测量系统。这种系统的一个例子是水置换方法，其中，在化学反应中产生的气体的体积是通过跟踪从一个倒置的充满水的量筒置换水的体积简单地进行测定。该技术起源于气动低谷，这是由植物学家斯蒂芬·黑尔斯开发，然后适应，并把它由约瑟夫·普利斯特里最有名的用于隔离的几种气体，包括氧气，在18 世纪 10,11水置换法适用于它是不溶于水，包括氢特别可溶的，并仍然被广泛用于记录从各种化学品，如硼氢化钠，铝和硅铁的反应产生氢气的体积，用水的任何气体。-12- 20 然而，经典的水中置换法，涉及在作为气体被放出的水位的变化人工记录，是乏味，并且可以在更高的气体流速，当水位急剧变化，是不准确的，因为它是难以实验者采取精确的读数。手工记录数据也是时间分辨率固有的低，作为实验者不能现实取读数更小的间隔比〜10秒。 一些研究人员通过使用摄像机来记录水位移过程和数据分析软件以提取在体积随时间的变化克服这个问题。21-25但是，该Requires计算机编程和相对昂贵的设备的知识。其他研究人员已经利用的质量流量计来记录氢气流26-29然而，这些往往只能够在一个窄的范围内检测气体，并且更适合于其中的流动被维持在一个相对恒定的应用水平。 以获得更高的分辨率更简单的方法，更准确的数据是到通道由氢气放出置换水进入其中放置在一个质量平衡接收机容器30-35本文描述该方法的变化是利用一般实验室级玻璃器皿和一种低成本，可商购天平从硅与氢氧化钠水溶液的反应记录析氢。而不是被手工记录，该数据被记录在使用数据收集软件包，它允许平衡发送数据到计算机中的电子表格。这应该注意，虽然该技术是适合于测量在毫升刻度析氢，它是不适合测量非常小（由于在平衡的不确定性），或非常大的（由于测量圆筒的大小有限）的卷氢气没有适当的调整（即使用更高的分辨率平衡或更大的量筒）。

<table><tbody><tr><td>WinWedge software</td><td>Taltech</td><td></td><td>http://www.taltech.com/winwedge</td></tr><tr><td>High Resolution Top Loader Balance</td><td>LW Measurements, LLC</td><td>HRB6001</td><td>http://www.lwmeasurements.com/HRB-6001-High-Resoultion-Top-Loader-Balance-p/hrb6001.htm</td></tr><tr><td>Silicon</td><td>Sigma Aldrich</td><td>215619</td><td>325 mesh</td></tr><tr><td>Sodium hydroxide</td><td>Sigma Aldrich</td><td>221465</td><td>Reagent grade</td></tr><tr><td>Aluminium (65.7%)-silicon (34.3%) alloy&amp;nbsp;</td><td>Goodfellow</td><td>275-274-74</td><td></td></tr><tr><td>Excel</td><td>Microsoft</td><td></td><td>https://products.office.com/en-us/excel</td></tr><tr><td>Glass sample vials, 50 x 12 mm</td><td>Scientific Laboratory Supplies</td><td>TUB1152</td><td></td></tr><tr><td>Plastic sheet</td><td></td><td></td><td>Recycled from a smooth-sided plastic drinks bottle</td></tr><tr><td>Silicone tubing, 5 x 8 mm BxO D</td><td>Scientific Laboratory Supplies</td><td>TUB3806</td><td></td></tr><tr><td>Parafilm (2 in. by 250 ft.)</td><td>Sigma Aldrich</td><td>P7543</td><td></td></tr><tr><td>Adapter</td><td>Sigma Aldrich</td><td>Z415685</td><td>We used a custom-made adapter in our set-up, but this type of fitting would serve the same function</td></tr></tbody></table>

a simple, low-cost, and robust system to measure the volume of hydrogen evolved by chemical reactions with aqueous solutions

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) hydrogen fuel cells. Researchers seeking to develop such systems require a method of measuring the generated hydrogen. Herein, we describe a simple, low-cost, and robust method to measure the hydrogen generated from the reaction of solids with aqueous solutions. The reactions are conducted in a conventional one-necked round-bottomed flask placed in a temperature controlled water bath. The hydrogen generated from the reaction in the flask is channeled through tubing into a water-filled inverted measuring cylinder. The water displaced from the measuring cylinder by the incoming gas is diverted into a beaker on a balance. The balance is connected to a computer, and the change in the mass reading of the balance over time is recorded using data collection and spreadsheet software programs. The data can then be approximately corrected for water vapor using the method described herein, and parameters such as the total hydrogen yield, the hydrogen generation rate, and the induction period can also be deduced. The size of the measuring cylinder and the resolution of the balance can be changed to adapt the setup to different hydrogen volumes and flow rates.

调查实验装置的再现性，变化的硅的质量，用氢氧化钠水溶液反应以产生氢。每个反应一式三份进行。平均氢产生曲线示于图1。平均总氢气产量，氢生成速率，并归纳为硅的各质量周期也计算并与表示在图2中，3个标准差误差棒被绘制， 和图4，分别。有在反应之间的总氢气产量和氢气产生率非常小的偏差和偏差的在诱导期更高水平。 <img alt="图1" src="/files/ftp_upload/54383/54383fig1.jpg" /> 图1: 从Reacti制氢曲线的实施例硅上用氢氧化钠水溶液的。硅的各种质量（0.05，0.10，0.15，0.20和0.25克），用氢氧化钠水溶液在50℃下进行反应（5毫升，20重量％）。氢产生被记录为一个周期的10分钟。该反应一式三份进行，结果取平均值。 <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/54383/54383fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图2" src="/files/ftp_upload/54383/54383fig2.jpg" /> 图 2: 从硅的用氢氧化钠水溶液反应氢气产量值的实施例的氢在10分钟内放出的总体积从氢产生曲线推导。获得并绘制为硅的各质量的平均总氢气产量。可以看出，有质量Ô之间的线性关系在反应和这些反应条件下产生的氢气的体积使用˚F硅。误差条表示总氢产量的一个标准差。 <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/54383/54383fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图3" src="/files/ftp_upload/54383/54383fig3.jpg" /> 图 3: 从硅用氢氧化钠水溶液反应制氢速率值的实施例从氢产生曲线计算氢产生的硅的各质量的初始或最大速率。得到的硅的各质量平均初始或最大氢产生速率和绘图。可以看出，平均而言，存在在反应中使用的硅的质量和初始或最大氢g之间功率关系<html>这些反应条件下观察到的eneration速率。误差条表示的初始或最大氢气生成速率的一个标准偏差。 <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/54383/54383fig3large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图4" src="/files/ftp_upload/54383/54383fig4.jpg" /> 图 4: 从硅用氢氧化钠水溶液反应诱导期值的实施例的氢产生硅的各质量的诱导期是从氢产生曲线推导。获得并绘制的平均诱导期为硅的各质量。可以看出，平均而言，有在实验之间的诱导期没有很大的变化。误差棒代表初始或最大氢气生成速率的一个标准偏差。REF ="htt​​ps://jove.unicartagenaproxy.elogim.com/files/ftp_upload/54383/54383fig4large.jpg"目标="_空白"&gt;点击此处查看该图的放大版本。 图5示出了从亚最佳实验一些代表性结果。在这种情况下，在滴液的积聚200和800秒的结果之间的氢气，由于水的表面张力的低流量，落在在大约400和710秒。虽然这些滴水不影响最大氢气生成速率的计算，如果，例如，测量停止的滴下降之前它们可能对总氢气产量的效果。因此，有必要要么改变反应条件（在此情况下，例如，通过加入铝 - 硅合金的较大的质量或使用的氢氧化钠的浓度较高），以确保气体的较高流动或反应设置，以防止滴的累积。 图5:一个次优实验例在本实验中，铝（65.7％） -硅（34.3％）的合金（0.2克）用氢氧化钠水溶液（5毫升，10重量％）在40℃下反应。虽然在氢气放出的初始高速率的氢产生的记录是最佳的，因为流动减慢形成的水的结果在滴的表面张力。该滴在处于大约400和710秒，在这种情况下， <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/54383/54383fig5large.jpg" target="_blank">请点击这里查看该图的放大版本。</a>

Watch this Scientific Journal Video about A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions at JoVE.com

A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions

The study of methods to generate on-demand hydrogen for fuel cells continues to grow in importance. However, systems to measure hydrogen evolution from the reaction of chemicals with water can be complicated and expensive. This article details a simple, low-cost, and robust method to measure the evolution of hydrogen gas.

一种简单，低成本和强大的系统来测量氢气与水溶液化学反应放出的音量

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) ...

a-simple-low-cost-robust-system-to-measure-volume-hydrogen-evolved

Universidad de Cartagena UDEC

Research

JoVE Journal

Chemistry

19.5K 次观看.  Loughborough University. The study of methods to generate on-demand hydrogen for fuel cells continues to grow in importance. However, systems to measure hydrogen evolution from the reaction of chemicals with water can be complicated and expensive. This article details a simple, low-cost, and robust method to measure the evolution of hydrogen gas.

视频: A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions

Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase

Understanding the chemistry of redox proteins demands methods that provide precise control over redox centers within the protein. The technique of protein film electrochemistry, in which a protein is immobilized on an electrode surface such that the electrode replaces physiological electron donors or acceptors, has provided functional insight into the redox reactions of a range of different proteins. Full chemical understanding requires electrochemical control to be combined with other techniques that can add additional structural and mechanistic insight. Here we demonstrate a technique, protein film infrared electrochemistry, which combines protein film electrochemistry with infrared spectroscopic sampling of redox proteins. The technique uses a multiple-reflection attenuated total reflectance geometry to probe a redox protein immobilized on a high surface area carbon black electrode. Incorporation of this electrode into a flow cell allows solution pH or solute concentrations to be changed during measurements. This is particularly powerful in addressing redox enzymes, where rapid catalytic turnover can be sustained and controlled at the electrode allowing spectroscopic observation of long-lived intermediate species in the catalytic mechanism. We demonstrate the technique with experiments on E. coli hydrogenase 1 under turnover (H2 oxidation) and non-turnover conditions.

Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase

Here, we describe a technique, protein film infrared electrochemistry, which allows immobilized redox proteins to be studied spectroscopically under direct electrochemical control at a carbon electrode. Infrared spectra of a single protein sample can be recorded at a range of applied potentials and under a variety of solution conditions.

用 [NiFe] 氢对 H2氧化的研究表明, 蛋白质膜红外电化学

Understanding the chemistry of redox proteins demands methods that provide precise control over redox centers within the protein. The technique of protein ...

科研

生物化学

Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and non-destructively reveals the hydrogen density distribution at surfaces, at interfaces, and in the volume of solid materials with high depth resolution. The technique applies a 15N ion beam of 6.385 MeV provided by an electrostatic accelerator and specifically detects the 1H isotope in depths up to about 2 &#956;m from the target surface. Surface H coverages are measured with a sensitivity in the order of ~1013 cm-2 (~1% of a typical atomic monolayer density) and H volume concentrations with a detection limit of ~1018 cm-3 (~100 at. ppm). The near-surface depth resolution is 2-5 nm for surface-normal 15N ion incidence onto the target and can be enhanced to values below 1 nm for very flat targets by adopting a surface-grazing incidence geometry. The method is versatile and readily applied to any high vacuum compatible homogeneous material with a smooth surface (no pores). Electrically conductive targets usually tolerate the ion beam irradiation with negligible degradation. Hydrogen quantitation and correct depth analysis require knowledge of the elementary composition (besides hydrogen) and mass density of the target material. Especially in combination with ultra-high vacuum methods for in-situ target preparation and characterization, 1H(15N,&#945;&#947;)12C NRA is ideally suited for hydrogen analysis at atomically controlled surfaces and nanostructured interfaces. We exemplarily demonstrate here the application of 15N NRA at the MALT Tandem accelerator facility of the University of Tokyo to (1) quantitatively measure the surface coverage and the bulk concentration of hydrogen in the near-surface region of a H2 exposed Pd(110) single crystal, and (2) to determine the depth location and layer density of hydrogen near the interfaces of thin SiO2 films on Si(100).

We illustrate the application of 1H(15N,&#945;&#947;)12C resonant nuclear reaction analysis (NRA) to quantitatively evaluate the density of hydrogen atoms on the surface, in the volume, and at an interfacial layer of solid materials. The near-surface hydrogen depth profiling of a Pd(110) single crystal and of SiO2/Si(100) stacks is described.

通过与核反应分析深度剖面的表面和界面层和颗粒材料氢含量的定量

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and ...

工程学

A Hydrogen-Deuterium Exchange Mass Spectrometry (HDX-MS) Platform for Investigating Peptide Biosynthetic Enzymes

Hydrogen-deuterium exchange mass spectrometry (HDX-MS) is a powerful method for the biophysical characterization of enzyme conformational changes and enzyme-substrate interactions. Among its many benefits, HDX-MS consumes only small amounts of material, can be performed under near native conditions without the need for enzyme/substrate labeling, and can provide spatially resolved information on enzyme conformational dynamics&#8722;even for large enzymes and multiprotein complexes. The method is initiated by the dilution of the enzyme of interest into buffer prepared in D2O. This triggers the exchange of protium in peptide bond amides (N-H) with deuterium (N-D). At the desired exchange time points, reaction aliquots are quenched, the enzyme is proteolyzed into peptides, the peptides are separated by ultra-performance liquid chromatography (UPLC), and the change in mass of each peptide (due to the exchange of hydrogen for deuterium) is recorded by MS. The amount of deuterium uptake by each peptide is strongly dependent on the local hydrogen bonding environment of that peptide. Peptides present in very dynamic regions of the enzyme exchange deuterium very rapidly, whereas peptides derived from well-ordered regions undergo exchange much more slowly. In this manner, the HDX rate reports on local enzyme conformational dynamics. Perturbations to deuterium uptake levels in the presence of different ligands can then be used to map ligand binding sites, identify allosteric networks, and to understand the role of conformational dynamics in enzyme function. Here, we illustrate how we have used HDX-MS to better understand the biosynthesis of a type of peptide natural products called lanthipeptides. Lanthipeptides are genetically encoded peptides that are post-translationally modified by large, multifunctional, conformationally dynamic enzymes that are difficult to study with traditional structural biology approaches. HDX-MS provides an ideal and adaptable platform for investigating the mechanistic properties of these types of enzymes.

A Hydrogen-Deuterium Exchange Mass Spectrometry HDX-MS Platform for Investigating Peptide Biosynthetic Enzymes

Lanthipeptide synthetases catalyze multistep reactions during the biosynthesis of peptide natural products. Here, we describe a continuous, bottom-up, hydrogen-deuterium exchange mass spectrometry (HDX-MS) workflow that can be employed to study the conformational dynamics of lanthipeptide synthetases, as well as other similar enzymes involved in peptide natural product biosynthesis.

氢-铀交换质谱仪（HDX-MS）平台，用于研究肽生物合成酶

Hydrogen-deuterium exchange mass spectrometry (HDX-MS) is a powerful method for the biophysical characterization of enzyme conformational changes and ...

A Practical and Low-Cost Setup to Measure Methane in Aqueous Samples

Measuring Dissolved Methane in Aquatic Ecosystems Using An Optical Spectroscopy Gas Analyzer

Measuring greenhouse gas (GHG) fluxes and pools in ecosystems are becoming increasingly common in ecological studies due to their relevance to climate change. With it, the need for analytical platforms adaptable to measuring different pools and fluxes within research groups also grows. This study aims to develop a procedure to use portable optical spectroscopy-based gas analyzers, originally designed and marketed for gas flux measurements, to measure GHG concentrations in aqueous samples. The protocol involves the traditional headspace equilibration technique followed by the injection of a headspace gas subsample into a chamber connected through a closed loop to the inlet and outlet ports of the gas analyzer. The chamber is fabricated from a generic mason jar and simple laboratory supplies, and it is an ideal solution for samples that may require pre-injection dilution. Methane concentrations measured with the chamber are tightly correlated (r2 &#62; 0.98) with concentrations determined separately through gas chromatography-flame ionization detection (GC-FID) on subsamples from the same vials. The procedure is particularly relevant for field studies in remote areas where chromatography equipment and supplies are not readily available, offering a practical, cheaper, and more efficient solution for measuring methane and other dissolved greenhouse gas concentrations in aquatic systems.

This study demonstrates an approach to measure methane gas concentrations in aqueous samples using portable optical analyzers coupled to an injection chamber in a closed loop. The results are similar to conventional gas chromatography, presenting a practical and low-cost alternative particularly suitable for remote field studies.

Measuring greenhouse gas (GHG) fluxes and pools in ecosystems are becoming increasingly common in ecological studies due to their relevance to climate ...

环境科学

Hydrogen Production and Utilization in a Membrane Reactor

Industrial hydrogenation consumes ~11 Mt of fossil-derived H2 gas yearly. Our group invented a membrane reactor to bypass the need to use H2 gas for hydrogenation chemistry. The membrane reactor sources hydrogen from water and drives reactions using renewable electricity. In this reactor, a thin piece of Pd separates an electrochemical hydrogen production compartment from a chemical hydrogenation compartment. The Pd in the membrane reactor acts as (i) a hydrogen-selective membrane, (ii) a cathode, and (iii) a catalyst for hydrogenation. Herein, we report the use of atmospheric mass spectrometry (atm-MS) and gas chromatography mass spectrometry (GC-MS) to demonstrate that an applied electrochemical bias across a Pd membrane enables efficient hydrogenation without direct H2 input in a membrane reactor. With atm-MS, we measured a hydrogen permeation of 73%, which enabled the hydrogenation of propiophenone to propylbenzene with 100% selectivity, as measured by GC-MS. In contrast to conventional electrochemical hydrogenation, which is limited to low concentrations of starting material dissolved in a protic electrolyte, the physical separation of hydrogen production from utilization in the membrane reactor enables hydrogenation in any solvent or at any concentration. The use of high concentrations and a wide range of solvents is particularly important for reactor scalability and future commercialization.

Membrane reactors enable hydrogenation in ambient conditions without direct H2 input. We can track the hydrogen production and utilization in these systems using atmospheric mass spectrometry (atm-MS) and gas chromatography mass spectrometry (GC-MS).

膜反应器中的氢气生产和利用

Industrial hydrogenation consumes ~11 Mt of fossil-derived H2 gas yearly. Our group invented a membrane reactor to bypass the need to use H2 gas for ...

化学

Introduction to Titration

Source: Laboratory of Dr. Yee Nee Tan &#8212; Agency for Science, Technology, and Research
Titration is a common technique used to quantitatively determine the unknown concentration of an identified analyte.1-4 It is also called volumetric analysis, as the measurement of volumes is critical in titration. There are many types of titrations based on the types of reactions they exploit. The most common types are acid-base titrations and redox titrations.5-11
In a typical titration process, a standard solution of titrant in a burette is gradually applied to react with an analyte with an unknown concentration in an Erlenmeyer flask. For acid-base titration, a pH indicator is usually added in the analyte solution to indicate the endpoint of titration.12 Instead of adding pH indicators, pH can also be monitored using a pH meter during a titration process and the endpoint is determined graphically from a pH titration curve. The volume of titrant recorded at the endpoint can be used to calculate the concentration of the analyte based on the reaction stoichiometry.
For the acid-base titration presented in this video, the titrant is a standardized sodium hydroxide solution and the analyte is domestic vinegar. Vinegar is an acidic liquid that is frequently used as a culinary condiment or flavorings. Vinegar mainly consists of acetic acid (CH3COOH) and water. The acetic acid content of commercial vinegar can vary widely and the goal of this experiment is to determine the acetic acid content of commercial vinegar by titration.

Titration: Principles, Volumetric Analysis

滴定法简介

Source: Laboratory of Dr. Yee Nee Tan &#8212; Agency for Science, Technology, and Research
Titration is a common technique used to quantitatively ...

教育

JoVE Science Education

普通化学

Determining Rate Laws and the Order of Reaction

Source: Laboratory of Dr. Neal Abrams &#8212; SUNY College of Environmental Science and Forestry
All chemical reactions have a specific rate defining the progress of reactants going to products. This rate can be influenced by temperature, concentration, and the physical properties of the reactants. The rate also includes the intermediates and transition states that are formed but are neither the reactant nor the product. The rate law defines the role of each reactant in a reaction and can be used to mathematically model the time required for a reaction to proceed. The general form of a rate equation is shown below:
&#160;&#160;&#160; <img alt="Equation 1" src="/files/ftp_upload/10193/10193eq1.jpg" />
where A and B are concentrations of different molecular species, m and n are reaction orders, and k is the rate constant. The rate of nearly every reaction changes over time as reactants are depleted, making effective collisions less likely to occur. The rate constant, however, is fixed for any single reaction at a given temperature. The reaction order illustrates the number of molecular species involved in a reaction. It is very important to know the rate law, including rate constant and reaction order, which can only be determined experimentally. In this experiment, we will explore one method for determining the rate law and use it to understand the progress of a chemical reaction.

确定率法律和秩序的反应

Source: Laboratory of Dr. Neal Abrams &#8212; SUNY College of Environmental Science and Forestry
All chemical reactions have a specific rate defining the ...

Catalytic Reactor: Hydrogenation of Ethylene

Source: <a href="https://jove.unicartagenaproxy.elogim.com/author/Kerry+M._Dooley">Kerry M. Dooley</a> and Michael G. Benton, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA
The hydrogenation of ethylene (C2H4) to ethane (C2H6) has often been studied as a model reduction reaction in characterizing new metal catalysts.1-2 While supported nickel is not the most active metal catalyst for this reaction, it is active enough that reaction can take place at &#60; 200&#176;C.
The reaction typically involves adsorbed, dissociated hydrogen (H2) reacting with adsorbed ethylene. In other words, both hydrogen-atoms and ethylene molecules form bonds with a metal site (here denoted &#34;S&#34;). The strong bonding of ethylene with S weakens the double bond sufficiently to allow hydrogen atoms to add to ethylene, forming ethane, which is not adsorbed.
The purpose of this experiment is, first, to convert raw composition measurements to limiting reactant fractional conversions.3 These conversions can then be used in a plug-flow reactor (PFR) to fit the data to a standard power-law kinetics model by the &#34;Integral Method&#34;.3 A comparison of the experimental orders of reaction for both ethylene and hydrogen with the theoretical orders reveals in this case that the reaction is kinetically controlled rather than mass-transfer controlled.

Heterogeneous Catalytic Reactor and Hydrogenation of Ethylene

催化反应器: 乙烯加氢

Source: Kerry M. Dooley and Michael G. Benton, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA
The hydrogenation of ...

化学工程

Measuring Reaction Rates

Polarimetry finds application in chemical kinetics to measure the concentration and reaction kinetics of optically active substances during a chemical reaction. Optically active substances have the capability of rotating the plane of polarization of linearly polarized light passing through them&#8212;a feature called optical rotation. Optical activity is attributed to the molecular structure of substances. Normal monochromatic light is unpolarized and possesses oscillations of the electrical field in all possible planes perpendicular to the direction of its propagation. When an unpolarized light passes through a polarizer, a linearly polarized light maintaining oscillations in one plane emerges out.
A polarimeter instrument determines the polarization direction of the light or the rotation produced by an optically active substance. In a polarimeter, the plane-polarized light is introduced to a tube containing the reacting solution, and the reaction can be followed without disturbing the system. If the sample contains optically inactive substances, there will be no change in the orientation of the plane of the polarized light. The light will be visible in the same intensity on the analyzer screen, and the angle of rotation reading (&#593;) will read zero degrees.
However, the presence of optically active compounds in the reacting sample causes the rotation of the plane of the polarized light passing through. The light emerging out will be less bright. The axis of the analyzer device will have to be rotated in a clockwise (dextrorotatory) or counter-clockwise (levorotatory) direction to observe the maximum brightness. The direction in which the analyzer needs to be rotated depends on the nature of the compound present. The optical rotation measured is proportional to the concentration of the optically active substances present in the sample. By analyzing the angle of rotation measurements at different time points, the concentrations of the optically active compounds can be determined as a function of time.
Spectrometry 
Optical experimental techniques like spectrometry are also frequently employed to monitor chemical reactions and secure quantitative information on reaction kinetics. Using spectrometry, the light of a specific wavelength is made to pass through a reacting sample. The molecules or compounds (either a reactant or product) within the sample may absorb some light while transmitting the remaining amount, which is measured by a detector. The quantity of light absorbed depends on the concentration of the compound or molecule of interest. For instance, the higher the concentration of a compound, the larger its absorbance. From the absorbance, the instrument will be able to determine the concentration of the compound of interest. In a reacting sample, the absorbance measured at periodic intervals computes the concentrations of the reactant or product as a function of time.
Pressure Measurements
For reactions involving gas-phase substances, the reaction kinetics is followed by quantifying the changes in the number of moles of gases as a function of the changes in pressure. The experimental settings of a gas-phase reaction can be connected to a manometer that could measure the pressure of either a gaseous reactant or product. As the reaction progresses, the pressure of the reactants decreases, and(or) the products&#39; pressure increases. This can be measured by the manometer as a function of time. By employing the ideal gas law&#8212;the concentration of a gas is proportional to its partial pressure&#8212;the rate of a chemical reaction can be calculated.

Experimental Techniques to Measure Reaction Rates

测量反应速率

Polarimetry finds application in chemical kinetics to measure the concentration and reaction kinetics of optically active substances during a chemical ...

JoVE Core

简介:物质与测量

化学动力学

关键术语与概念

Constant Pressure Calorimetry

Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a substance. The heat is exchanged with a calibrated and insulated device called the calorimeter. Calorimetry experiments are based on the assumption that there is no heat exchange between the insulated calorimeter and the external environment. The well-insulated calorimeters prevent the transfer of heat between the calorimeter and its external environment, which effectively limits the &ldquo;surroundings&rdquo; to the nonsystem components within the calorimeter (and the calorimeter itself). This enables the accurate determination of the heat involved in chemical processes, such as the energy content of foods.&nbsp;
The temperature change measured by the calorimeter is used to derive the amount of heat transferred by the process under study. In a calorimeter, a system is defined as the substance or substances undergoing the chemical or physical change, or in other words, the reaction, and the surroundings are all other matter, including the solution and any other components in the calorimeter that either provide heat to the system or absorb heat from the system.
Before discussing the calorimetry of chemical reactions, consider a simpler example that illustrates the core idea behind calorimetry. Suppose a hot piece of metal at a high-temperature is placed in a low-temperature substance, such as cool water. Heat will flow from the hot metal to the water. The temperature of the metal will decrease, and the temperature of the water will increase until the two substances have the same temperature&mdash;that is when they reach thermal equilibrium. If this occurs in a calorimeter, all of the heat is transferred between the two substances, with no heat gained or lost by its external environment. Under these ideal circumstances, the net heat change is zero:
<img alt="Eq1" src="https://jove.unicartagenaproxy.elogim.com/files/core/CDNSource/lessons/798/798_Equations-01.png" style="height: 40px;" />
This relationship can be rearranged to show that the heat gained by the metal is equal to the heat lost by substance the water:
<img alt="Eq2" src="https://jove.unicartagenaproxy.elogim.com/files/core/CDNSource/lessons/798/798_Equations-02.png" style="height: 40px;" />
The magnitude of the heat (change) is, therefore, the same for both substances. The negative sign merely shows that qmetal and qwater are opposite in direction of&nbsp;heat flow (gain or loss), but it does not indicate the arithmetic sign of either q value (that is determined by whether the matter in question gains or loses heat, per definition). In the specific situation described, qmetal is a negative value and qwater is a positive value since heat is transferred from the metal to the water.
When using calorimetry to determine the heat involved in a chemical reaction, the same principles apply. The amount of heat absorbed by the calorimeter is often small enough that it can most often be neglected, and the calorimeter minimizes energy exchange with the outside environment. When an exothermic reaction occurs in solution in a calorimeter, the heat produced by the reaction is absorbed by the solution, which increases its temperature. When an endothermic reaction occurs, the heat required is absorbed from the thermal energy of the solution, which decreases its temperature. The temperature change (&Delta;T), along with the specific heat (csoln) and mass of the solution (msoln), can then be used to calculate the amount of heat (qsoln) involved in either case.
<img alt="Eq3" src="https://jove.unicartagenaproxy.elogim.com/files/core/CDNSource/lessons/798/798_Equations-03.png" style="height: 40px;" />
A &nbsp;simple calorimeter &mdash; called the coffee cup calorimeter &mdash; is constructed from two nested polystyrene cups closed with a loose-fitting lid. Coffee cup calorimeters are used to measure the heat of reactions that take place in solutions (mostly aqueous solutions) and involve no or very little volume change. Because energy is neither created nor destroyed during a chemical reaction, the heat produced or consumed in the reaction (the &ldquo;system&rdquo;), qrxn, plus the heat absorbed or lost by the solution (the &ldquo;surroundings&rdquo;), qsoln, must add up to zero:
<img alt="Eq4" src="https://jove.unicartagenaproxy.elogim.com/files/core/CDNSource/lessons/798/798_Equations-04.png" style="height: 40px;" />
This means that the amount of heat produced or consumed in the reaction equals the amount of heat absorbed or lost by the solution:
<img alt="Eq5" src="https://jove.unicartagenaproxy.elogim.com/files/core/CDNSource/lessons/798/798_Equations-05.png" style="height: 40px;" />
The coffee cup calorimeter is a constant-pressure calorimeter, and the measured heat of the reaction is equivalent to the change in enthalpy.
<img alt="Eq6" src="https://jove.unicartagenaproxy.elogim.com/files/core/CDNSource/lessons/798/798_Equations-06.png" style="height: 40px;" />
This text is adapted from <a href="https://openstax.org/books/chemistry-2e/pages/5-2-calorimetry">Openstax, Chemistry 2e, Section 5.2: Calorimetry</a>.

Constant Pressure Calorimeter/ Coffee Cup Calorimeter

恒压量热法

Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a ...