摘要
氢能因具有储量丰富、零排放和可再生等优点,受到各国在能源布局过程中的广泛关注.制氢是氢能源开发和利用的重要环节,其中电解水制氢技术可通过低能耗水分解获得氢气,具有很高的社会效益和经济效益.在电解水过程中,由于受析氧反应(OER)的缓慢动力学过程限制,电解水制氢体系在碱性介质中的理论工作电压高达1.23 V,增加了制氢能耗.在使用电化学催化剂的同时采用具有低热力学电势(0.37 V)的尿素氧化反应(UOR)代替OER,可降低制氢过程的能耗.本文采用水热反应结合煅烧反应在泡沫镍上生长了海胆状NiMoO_(4)纳米棒阵列,并将其作为双功能电催化剂,用于阴极析氢和阳极尿素氧化反应.结果表明,200℃煅烧产物(NiMoO_(4)-200/NF)表现出高效的析氢反应(HER)性能,在1.0 mol/L KOH中电流密度为10 mA cm^(-2)时的过电位仅为68 mV.而300℃煅烧产物(NiMoO_(4)-300/NF)表现出优异的析氧反应和尿素氧化反应活性.为了探究NiMoO_(4)纳米棒阵列在不同反应中催化性能差异的原因,通过各种表征手段对催化剂进行了结构及组成的表征.X射线衍射与高分辨透射电镜结果表明,200和300℃下的煅烧产物由NiMoO_(4)与NiMoO_(4)·xH_(2)O组成,而煅烧温度变化引起的电催化活性和选择性的差异则归因于产物不同的晶格氧含量.X射线光电子能谱结果表明,NiMoO_(4)-300/NF比NiMoO_(4)-200/NF含有更多的晶格氧;而对于高价态金属氧化物而言,催化剂中的晶格氧在电氧化过程中可以被激活并直接参与到阳极氧化反应过程,从而有利于析氧反应和尿素氧化反应的进行.另外,以NiMoO_(4)-300/NF和NiMoO_(4)-200/NF作为阳极和阴极组装尿素电解槽,可在1.38 V的电池电压下提供10 mA cm^(–2)的电流密度.将电极与商品太阳能板连接,NiMoO_(4)纳米棒阵列双电极可成功实现光电压驱动的尿素电解和制氢,表明其在太阳能驱动的能量转换方面具有巨大潜力.
Developing multifunctional electrocatalysts with high catalytic activity,longterm stability,and low cost is essential for electrocatalytic energy conversion.Herein,sea urchinlike NiMoO_(4) nanorod arrays grown on nickel foam has been developed as a bifunctional electrocatalyst for urea oxidation and hydrogen evolution.The NiMoO_(4)‐200/NF catalyst exhibits efficient activity toward hydrogen evolution reaction with a low overpotential of only 68 mV in 1.0 mol/L KOH to gain a current density of 10 mA cm^(–2).The NiMoO_(4)‐300/NF catalyst exhibits a prominent oxygen evolution reaction(OER)catalytic activity with an overpotential of 288 mV at 50 mA cm^(–2),as well as for urea oxidation reaction with an ultralow potential of 1.36 V at 10 mA cm^(–2).The observed difference in electrocatalytic activity and selectivity,derived by temperature variation,is ascribed to different lattice oxygen contents.The lattice oxygen of NiMoO_(4)‐300/NF is more than that of NiMoO_(4)‐200/NF,and the lattice oxygen is conducive to the progress of OER.A urea electrolyzer was assembled with Ni‐MoO_(4)‐200/NF and NiMoO_(4)‐300/NF as cathode and anode respectively,delivering a current density of 10 mA cm^(–2)at a cell voltage of merely 1.38 V.The NiMoO_(4)nanorod arrays has also been successfully applied for photovoltage‐driven urea electrolysis and hydrogen production,revealing its great potential for solar‐driven energy conversion.
作者
陈晨欣
何苏祺
Kamran Dastafkan
邹泽华
汪庆祥
赵川
Chenxin Chen;Suqi He;Kamran Dastafkan;Zehua Zou;Qingxiang Wang;Chuan Zhao(Department of Chemistry and Environment Science,Fujian Provincial Key Laboratory of Modern Analytical Science and Separation Technology,Minnan Normal University,Zhangzhou 363000,Fujian,China;School of Chemistry and Materials&Manufacturing Futures Institute,The University of New South Wales,Sydney 2052,Australia)
基金
澳大利亚研究委员会未来研究基金(FT170100224)
国家自然科学基金(21275127)
福建省自然科学基金(2018J01435).
