一体化电极电催化二氧化碳还原研究进展

Recent Advances in Integrated Electrode for Electrocatalytic Carbon Dioxide Reduction

电催化二氧化碳还原反应(E-CO_(2)RR)可在温和条件下将CO_(2)转化成高附加值燃料或化学品,近年来受到广泛关注,其在实际反应中涉及到气体扩散和多电子转移等复杂过程,构筑高效、稳定的催化电极是其发展的核心之一。然而,传统涂敷电极制备时,需要将催化剂与粘结剂混合涂覆于集流体表面,此过程会造成活性位点包埋和传质过程受限,致使催化剂活性位利用率下降,同时在反应过程中电极表面容易粉化,造成稳定性下降,难以重复利用。因此,如何调控电极反应界面,提升催化剂活性位的利用率仍面临挑战。将催化剂原位生长于集流体上得到的一体化电极可直接应用于电催化反应,不仅有利于提升活性位利用率以及电荷传输能力,还能有效调控三相界面处的微观反应环境(如pH、反应物及反应中间体的浓度等),从而实现电催化性能强化。本文综述了一体化电极用于E-CO_(2)RR的最新进展,分析了结构和表界面调控对E-CO_(2)RR性能的影响规律,并对该领域仍然存在的挑战和未来一体化E-CO_(2)RR电极的发展进行了评述与展望。

The electrocatalytic carbon dioxide reduction reaction(E-CO_(2)RR)has attracted attention in recent years for its ability to effectively alleviate the environmental problems caused by the rapid increase of CO_(2)in the atmosphere and transform CO_(2)into high value-added fuels or chemicals(e.g.,CO,HCOOH,CH_(4),CH_(3)OH,C_(2)H_(4),C_(2)H_(5)OH,etc.)under mild conditions.In addition,clean energy sources,such as solar and wind energy,can provide electrical energy for the electrochemical CO_(2) conversion technology used in large-scale industrial applications.One limitation of the E-CO_(2)RR is that CO_(2) is a thermodynamically stable linear molecule with a slow kinetic reaction rate.In addition,the E-CO_(2)RR involves complex processes,such as gas diffusion and multi-electron transfer,making its selectivity problematic.Therefore,constructing highly efficient and stable catalytic electrodes has become a core research topic in the field of E-CO_(2)RR.Unfortunately,the traditional method of coating electrodes with binders(e.g.,Nafion,polyvinylidene fluoride,and polytetrafluoroethylene)usually results in a low utilization ratio of active sites due to the easy aggregation of the catalysts themselves.This could result in the severe embedding of active sites and limited mass transfer.Moreover,the dissolution of the catalyst layer during the electrocatalytic process also reduces the activity and stability of the electrodes,making it difficult to reuse.Therefore,it is necessary to regulate the electrode reaction interface to improve the utilization ratio of active sites.The integrated electrodes,where the catalyst is grown directly on the current collector,can avoid the use of binders to facilitate the exposure of active sites and transfer of electrons.The integrated structure can also enhance the bonding strength between the active material and current collector and improve the cycling stability of the electrodes.Meanwhile,the micro-environment(e.g.,pH,concentration of CO_(2),and intermediates)at the three-phase interface can be effectively controlled on the integrated electrodes,which can enhance the performance of the E-CO_(2)RR.In recent years,encouraging progress has been achieved in the study of the E-CO_(2)RR.However,current reviews of the E-CO_(2)RR mainly focus on the regulation of the intrinsic activity of catalysts;discussions and reviews from the perspective of the electrodes are rarely reported.This article reviews the latest research of the integrated electrodes for the E-CO_(2)RR with a focus on the application of different types of integrated electrodes(e.g.,metal,alloy,metal oxide,metal sulfide/phosphide,and metal single atom).It also analyzes the effects of morphology,surface,and interface regulation on the electrocatalytic performance of the E-CO_(2)RR.Finally,it highlights the challenges that still exist in this field and discusses the future development of the integrated electrodes.