电催化二氧化碳还原催化剂、电解液、反应器和隔膜研究进展

Research Advances in Electrocatalysts,Electrolytes,Reactors and Membranes for the Electrocatalytic Carbon Dioxide Reduction Reaction

人类社会的正常运转非常依赖化石能源,然而化石能源的消耗已导致能源危机和环境污染,同时空气中CO_(2)的含量从工业革命以来一直攀升。将CO_(2)通过催化反应转化为高附加值的燃料和化学品,不仅可以缓解环境问题,还开辟了一种燃料合成新路径,其中电催化CO_(2)还原技术由于条件温和、反应可控、对环境友好和产物众多受到广泛关注。电催化CO_(2)技术有四个关键步骤:(1)电荷传输(电子从导电基底传输到电催化剂);(2)表面转化(CO_(2)吸附在催化剂表面并被活化);(3)电荷传输(电子从催化剂表面传输到CO_(2)中间体);(4)传质效应(CO_(2)从电解质扩散到催化剂表面,产物以反向路径扩散),前两个步骤依赖于具有丰富有效活性位点的催化剂,后两个步骤依赖于电解质的性质、隔膜的类型和电解池的配置。本文从工业化和商业化电催化CO_(2)技术出发,系统地归纳催化剂的发展、电解液的影响、反应器的进展和隔膜的类型,最后对电催化CO_(2)还原的产业化进行展望。

Human activities primarily rely on the consumption of the fossil energy,which has led to an energy crisis and environmental pollution.Since the industrial revolution,the atmospheric CO_(2) concentration has been continuously increasing,and reached 414×10^(−6) in 2020,which has resulted in global warming and glacial ablation.Converting CO_(2) into high-value-added fuels and chemicals can alleviate environmental problems,enable the storage of intermittent renewable energy(wind and solar power),and provide a new route for fuel synthesis.The electrochemical CO_(2) reduction reaction(CO_(2)RR)has attracted extensive attention owing to its mild reaction conditions,controllability,environmental friendliness,and the ability to generate various products.There are four key steps in a typical CO_(2)RR:(1)charge transport(electrons are transported from the conductive substrate to the electrocatalyst);(2)surface conversion(CO_(2) is adsorbed and activated on the surface of the catalyst);(3)charge transfer(electrons are transferred from the catalyst surface to the CO_(2) intermediate);and(4)mass transfer(CO_(2) diffuses from the electrolyte to the catalyst surface,and the products diffuse in the reverse pathway).The former two steps depend on the type of membrane and the development of highly conductive catalysts with abundant active sites,while the latter two steps rely on the properties of the electrolyte and the optimization of the electrolytic cell configuration.To meet the high-selectivity(>90%),superioractivity(>200 mA∙cm^(−2)),and excellent-stability(>1000 h)requirements of the CO_(2)RR as per industrial standards,the design of efficient electrocatalysts has been a key research area in recent decades.However,other factors have rarely been investigated.In this review,we systematically summarize the development of electrocatalysts,effect of the electrolyte,progress in the development of the reactor,and type of membrane in the CO_(2)RR from industrial and commercial perspectives.First,we discuss how first-principles calculations can be used to determine the chemical rate for CO_(2) reduction.Additionally,we discuss how in situ or operando techniques such as X-ray absorption measurements can reveal the theoretically proposed reaction pathway.The microenvironment(e.g.,pH,anions,and cations)at the three-phase interface plays a vital role in achieving a high CO_(2)RR performance,which can be controlled by changing the electrolyte properties.Further,the suitable design and development of the reactor is very critical for commercial CO_(2)RR technology because CO_(2)RR reactors must efficiently utilize the CO_(2) feedstock to minimize the cost of upstream CO_(2) capture.Finally,different types of membranes based on different ion-transfer mechanisms can affect the CO_(2)RR performance.The development opportunities and challenges toward the practical application of the CO_(2)RR are also highlighted.