多孔Cu_(2)O立方体电催化还原CO_(2)制备乙烯/乙醇

Preparation of ethylene/ethanol by electrocatalytic reduction of CO_(2) with porous Cu_(2)O cube

铜基催化剂能够有效地将二氧化碳电化学还原为多碳C_(2+)产物,催化剂的组成和结构是影响C_(2+)产物催化活性和选择性的重要因素。本研究旨在考察Cu_(2)O催化剂多孔结构对电化学还原CO_(2)的C_(2)产物选择性的影响。首先通过酸刻蚀实心Cu_(2)O立方体(S-Cu_(2)O)制备了具有多孔结构的Cu_(2)O立方体(P-Cu_(2)O)。SEM、TEM、XRD、XPS和CV等表征结果表明,S-Cu_(2)O和P-Cu_(2)O的组成相同,为混合Cu价态Cu(0)和Cu(I)。2者形貌为约180 nm立方体,而P-Cu_(2)O具有不规则的空腔型多孔结构。电化学表征结果表明,P-Cu_(2)O的电化学活性表面积约为S-Cu_(2)O的1.75倍,且界面电荷转移电阻比S-Cu_(2)O低。在N_(2)和CO_(2)氛围下的线性伏安扫描(LSV)结果表明P-Cu_(2)O具有更高的CO_(2)催化活性。在气体扩散电极-流动电解池体系进行不同电位下催化剂的电催化还原CO_(2)反应,考察多孔结构对CO_(2)还原活性和C_(2)产物选择性的影响,结果表明,在电位为-1.0 V vs.RHE,电解质为2 mol·L^(-1)KOH时,P-Cu_(2)O的CO_(2)还原产物选择性达37.7%(C_(2)H_(4):25.6%,C_(2)H_(5)OH:12.1%),分电流密度达20.9 mA·cm^(-2),比S-Cu_(2)O提高了~28%。以^(∗)COR/[^(∗)COR/CO_((g))]计算关键中间体^(∗)CO深度转化率,结果表明P-Cu_(2)O的^(∗)CO深度转化明显高于S-Cu_(2)O。综上,P-Cu_(2)O对C_(2)产物选择性的提高归因于:多孔结构使P-Cu_(2)O具有高活性表面积,提供更多的CO_(2)还原活性位点,促进CO生成;空腔的结构有利于∗CO局域浓度提高,加速∗CO二聚反应生成C_(2)产物。为设计和开发电催化还原二氧化碳制多碳产物的Cu_(2)O基高效催化剂具有重要意义。

Cu_(2)O catalyst can effectively electrochemically reduce carbon dioxide to multi carbon C_(2+)products.The composition and structure of the catalyst are important factors affecting the catalytic activity and selectivity of C_(2+)products.The purpose of this study was to investigate the effect of porous structure of Cu_(2)O catalyst on the selectivity of C_(2)products for electrochemical reduction of CO_(2).Firstly,Cu_(2)O cubes with porous structure(P-Cu_(2)O)were prepared by acid etching solid Cu_(2)O cubes(S-Cu_(2)O).SEM,TEM,XRD,XPS,CV and other characterization results show that the composition of S-Cu_(2)O and PCu_(2)O is the same,and they are mixed Cu valence:Cu0 and Cu+.The morphology of both is about 180 nm cube,while P-Cu_(2)O has irregular cavity porous structure.The electrochemical characterization results show that the electrochemical active surface area of P-Cu_(2)O is about 1.75 times that of S-Cu_(2)O,and the interfacial charge transfer resistance is lower than that of S-Cu_(2)O.Linear voltammetric scanning(LSV)results in N_(2)and CO_(2)atmosphere showed that P-Cu_(2)O had higher CO_(2)catalytic activity.The electrocatalytic reduction of CO_(2)was carried out under different potentials in the gas diffusion electrode flow cell system.The effects of porous structure on CO_(2)reduction activity and C_(2)product selectivity were investigated.The results showed that when the potential was-1.0 V vs.RHE and the electrolyte was 2 mol·L^(-1)KOH,the CO_(2)reduction product selectivity of P-Cu_(2)O was 37.7%(C_(2)H_(4):25.6%,C_(2)H_(5)OH:12.1%),and the partial current density was 20.9 mA·cm^(-2),which was~28%higher than that of S-Cu_(2)O.The deep conversion of key intermediate^(∗)CO was calculated by^(∗)COR/[^(∗)COR/CO_((g))].The results showed that the deep conversion of^(∗)CO of P-Cu_(2)O was significantly higher than that of S-Cu_(2)O.In conclusion,the improvement of the selectivity of P-Cu_(2)O for C_(2)products is attributed to:the porous structure makes P-Cu_(2)O have high active surface area,provides more CO_(2)reduction active sites and promotes the formation of CO;the structure of the cavity is conducive to increase the local concentration of^(∗)CO and accelerate the dimerization of^(∗)CO to produce C_(2)product.This study is of great significance for the design and development of Cu_(2)O based high-efficiency catalysts for electrocatalytic reduction of carbon dioxide to multi carbon products.