基于单原子催化剂的二氧化碳选择性转化

Selective Conversion of CO_(2) by Single-Site Catalysts

近年来,由于其接近100%的原子利用率和独特的催化性能,单原子催化剂研究受到了极大的关注。近年来,人们针对二氧化碳选择性催化转化的单原子催化剂研究开展了大量的工作,实现了一氧化碳、甲烷、甲醇、甲酸以及C_(2+)化合物等化学品的选择性合成。此外,通过引入胺类以及环氧化合物,二氧化碳可以催化转化为高附加值的精细化学品。本综述总结了近几年来单原子催化剂通过电催化、光催化以及热催化的方法在二氧化碳选择性还原方面的研究工作,并深入探讨单原子催化剂在二氧化碳选择还原反应中的结构性能关系以及其结构的调控对催化剂活性的影响。

Industrial revolution has led to increased combustion of fossil fuels.Consequently,large amounts of CO_(2) are emitted to the atmosphere,throwing the carbon cycle out of balance.Currently,the most effective method to reduce the CO_(2) concentration is direct CO_(2) capture from the atmosphere and pumping of the captured CO_(2) deep underground or into the mid-ocean.The transformation of CO_(2)into high-value chemicals is an attractive yet challenging task.In recent years,there has been much interest in the development of CO_(2) utilization technologies based on electrochemical CO_(2) reduction,photochemical CO_(2) reduction,and thermal CO_(2)reduction,and CO_(2) valorization has emerged as a hot research topic.In electrochemical CO_(2) reduction,the cathodic reaction is the reduction of CO_(2) to value-added chemicals.The anodic reaction should be the oxygen evolution reaction,and water is the only renewable and scalable source of electrons and protons in this reaction.There is a plethora of research on the use of various metals to catalyze this reaction.Among these,Cu-based materials have been demonstrated to show unique catalytic activity and stability for the electrochemical conversion of CO_(2) to valuable fuels and chemicals.Moreover,the solar-driven conversion of CO_(2) into value-added chemical fuels has attracted great attention,and much effort is being devoted to develop novel catalysts for the photoreduction of CO_(2),especially by mimicking the natural photosynthetic process.The key step in the photocatalytic process is the efficient generation of electron-hole pairs and separation of these charge carriers.The efficient separation of photoinduced charge carriers plays a crucial role in the final catalytic activity.Compared with CO_(2) reduction via electrocatalysis and photocatalysis,thermal reduction is more attractive because of its potential large-scale application in the industry.Heterogeneous nanomaterials show excellent activity in the electrocatalytic,photocatalytic,and thermal catalytic conversion of CO_(2).However,nanostructured materials have drawbacks on the investigation of the intrinsic activity of the active sites.In recent years,single-site catalysts have become popular because they allow for maximum utilization of the metal centers,show specific catalytic performance,and facilitate easy elucidation of the catalytic mechanism at the molecular level.Accordingly,numerous single-site catalysts were developed for CO_(2) reduction to produce value-added chemicals such as CO,CH4,CH3OH,formate,and C2+products.Value-added chemicals have also been synthesized with the aid of amines and epoxides.This review summarizes recent state-of-the-art single-site catalysts and their application as heterogeneous catalysts for the electroreduction,photoreduction,and thermal reduction of CO_(2).In the discussion,we will highlight the structure-activity relationships for the catalytic conversion of CO_(2) with single-site catalysts.