脉冲电催化的研究进展及性能强化机制

Recent Advances and Performance Enhancement Mechanisms of Pulsed Electrocatalysis

基于电催化的能源转化、化学品合成及污染物降解技术是解决能源与环境问题的重要方式.一些研究已经证明,通过简单地施加周期性切换电位的脉冲供电策略,将会有效提升电催化性能.本文对脉冲供电策略在电化学高级氧化、电化学二氧化碳还原、有机电合成、电解水制氢等经典电化学体系中的应用及研究进展进行了综述,并具体分析了其对各类电催化反应性能的强化机制,这些机制主要包括:通过周期性更新能斯特扩散层的物质浓度以增强催化活性;通过动态调控中间体吸附能以提高催化选择性;通过维持催化剂表面处于非平衡状态,避免催化剂失活以提高催化剂的稳定性.最后,本文展望了脉冲电催化未来所面临的机遇与挑战.

Due to the excessive exploitation and utilization of fossil fuels,we are faced with severe energy and environmental problems.Therefore,it’s significant to develop electrocatalytic energy conversion,chemical synthesis and pollutant degradation technologies.In order to achieve high activity,selectivity and stability of electrocatalytic reactions,researchers have made a lot of efforts in catalyst design,interface microenvironment regulation and reactor structure optimization.In fact,there is still a wide space on the power supply side for the regulation of electrocatalytic system.Although most researchers choose to use potentiostatic or galvanostatic power supply strategy,some studies have proven that the pulsed power supply strategy by implementing altering potential periodically can improve electrocatalytic performance to a great extent.Compared with traditional regulating methods mentioned above,the pulsed electrocatalysis is much simpler,efficient and repeatable because it just needs to modulate the output potential or current mode.In addition,it is more favorable to be coupled with smart energy in the future.Therefore,the pulsed electrocatalysis has broad development prospects.In this review,we summarized the application and recent progress of the pulsed power supply strategy in classical electrocatalytic systems include electrochemical advanced oxidation processes,electrochemical carbon dioxide reduction,organic electrochemical synthesis,hydrogen production through water electrolysis.Besides,we analyzed the enhancement mechanisms of pulsed electrocatalysis.These enhancement mechanisms can be generalized as follows:(1)By updating the concentration of substance in Nernst diffusion layer during the implementation of switching potential periodically,the concentration polarization can be prevented.Thus,the electrocatalytic activity can be enhanced.Besides,some side reactions caused by mass transfer restriction can also be suppressed.(2)Through altering the adsorption energy of the reaction intermediate and adjusting the coverage of intermediate on the catalyst surface under oscillating potential periodically,the electrocatalytic selectivity of target reaction can be increased.Furthermore,because the active site of catalyst can be modulated to alternate between ideal states for adsorption of intermediate and desorption of product,the Sabatier’s theoretical limit on static catalytic site may be breached and the turnover frequency(TOF)of the catalyst can increase by several orders of magnitude during the pulsed dynamic electrocatalysis process.(3)The catalyst surface can be kept in a non-equilibrium state to avoid the inactivation caused by excessive oxidation or reduction of active site or the deposition of some toxic substances on the surface of a catalyst.Thus,the electrocatalytic stability will be improved.Besides,the dynamic reconfiguration of catalysts during pulsed electrocatalysis will influence the activity and selectivity of reaction.Finally,we prospect for the challenges and opportunities of pulsed electrocatalysis in the future.