电催化CO2还原合成C2+产物的机理和材料研究进展

Progress in the Mechanisms and Materials for CO2 Electroreduction toward C2+ Products

过去几十年里,科学技术的进步为人类社会带来了巨大便利。然而,化石燃料的过度开发和污染物的过量排放打破了先前碳循环的平衡,引起了严重的环境和能源危机。其中,CO2过度排放是导致全球变暖的重要原因,因此降低大气中CO2浓度迫在眉睫。在众多CO2转化途径中,电催化CO2还原,特别是在生成具有高附加值C2+产物方面,表现出较大潜力,近年来备受关注。当前,在电催化CO2还原合成C2+产物的材料方面取得了很大进展,但是存在一些科学问题亟待解决,例如:低的选择性,低的电流效率,低的耐久性。此外,电催化CO2还原合成C2+产物的基本反应机理也尚不清楚。对此,本文对电催化CO2还原合成C2+产物过程中一些典型的材料调控策略以及工艺设计进行了简单而清晰的总结(例如:晶面调制,缺陷工程,尺寸效应,限域效应,电解槽设计,电解质p H)。在此基础上,最后讨论了未来电催化CO2还原合成C2+产物的挑战和前景。

Over the past decades,advances in science and technology have greatly benefitted the society.However,the exploitation of fossil fuels and excessive emissions of polluting gases have disturbed the balance of the normal carbon cycle,causing serious environmental issues and energy crises.Global warming caused by heavy CO2emissions is driving new attempts to mitigate the increase in the concentration of atmospheric CO2.Significant efforts have been devoted for CO2 conversion.To date,the electroreduction of CO2,which is highly efficient and offers a promising strategy for both storing energy and managing the global carbon balance,has attracted great attention.In addition,the electrosynthesis of value-added C2+products from CO2 addresses the need for the long-term storage of renewable energy.Therefore,developing catalysts that function under ambient conditions to produce C2 selectively over C1 products will increase the utility of renewable feedstocks in industrial chemistry applications.Recently,great progress has been made in the development of materials for electrocatalytic CO2reduction(ECR)toward C2+products;however,some issues(e.g.,low selectivity,low current efficiency,and poor durability)remain to be addressed.In addition,the elementary reaction mechanism of each C2+product remains unclear,contributing to the blindness of catalyst design.In this regard,the development of proposed mechanisms of ECR toward C2+products is summarized herein.The key to generating C2+products is improving the chances of C―C coupling.Test conditions significantly influence the reaction path of the catalyst.Thus,three different paths that that are most likely to occur during ECR to C2+products are proposed,including the CO,CO-COH,and CO-CO paths.In addition,typical material regulatory strategies and technical designs for ECR toward C2+products(e.g.crystal facet modulation,defect engineering,size effect,confinement effects,electrolyzer design,and electrolyte p H)are introduced,focusing on their effects on the selectivity,current efficiency,and durability.The four strategies for catalyst design(crystal facet modulation,defect engineering,size effect,and confinement effect)primarily affect the selectivity of the ECR via adjustment of the adsorption of reaction intermediates.The last two strategies for technique design(electrolyzer design and electrolyte p H)contributing greatly toward improving the current efficiency than selectivity.Finally,the challenges and perspectives for ECR toward C2+products and their future prospects are discussed herein.Therefore,breakthroughs in the promising field of ECR toward the generation of C2+products are possible when these catalyst design strategies and mechanisms are applied and novel designs are developed.