Controlling the Oxidation State of the Cu Electrode and Reaction Intermediates for Electrochemical CO₂ Reduction to Ethylene

Abstract

Understanding the role of oxidation state of Cu surface and surface-adsorbed intermediate species in electrochemical CO2 reduction is crucial for the development of selective CO2-to-fuel electrocatalysts. In this study, the electrochemical CO2 reduction mechanism over the Cu catalysts with various oxidation states was studied by using in situ surface-enhanced infrared absorption spectroscopy (SEIRAS), in situ soft X-ray absorption spectroscopy (Cu L-edge) and on-line gas chromatography measurements. The atop-adsorbed CO (COatop) intermediate is obtained on the electrodeposited Cu surface which primarily has the oxidation state of Cu(I). COatop is further reduced, followed by the formation of C1 product such as CH4. The residual bridge-adsorbed CO (CObridge) is formed on the as-prepared Cu surface with Cu(0) which inhibits hydrocarbon formation. In contrast, the CV-treated Cu electrode prepared by oxidizing the as-prepared Cu surface contains different amount of Cu(I) and Cu(0) states. The major theme of this work is that in situ SEIRAS results show the coexistence of COatop and CObridge as the reaction intermediates during CO2 reduction and the selectivity of CO2-to-ethylene conversion is further enhanced in the CV-treated Cu electrode. The Cu catalysts modulated by electrochemical method exhibit different oxidation states and reaction intermediates as well as the electrocatalytic properties.

Cu-Ag Tandem Catalysts for High-Rate CO2 Electrolysis toward Multicarbons

“…Although the Cu LMM Auger peak indicates that the surface of nano powder has been oxidized, numerous studies [40][41][42][43][44] indicate that such a naturally formed oxide shell can be quickly reduced under working condition. Despite the ongoing debate in the community towards the existence and function of oxygen residue during CO2RR [45][46][47] , we note that such a phenomenon will not influence the conclusions related to tandem interactions between Ag and Cu of the later discussion in this work. Meanwhile, it is widely reported that Cu can undergo surface reconstruction and structural evolution during CO2 electrolysis, [48][49][50][51] and previous reports have also invoked Cu-Ag alloy [13][14][15] or surface alloy 16 strategies to im-To further probe the role of local CO towards the C2+ enhancement, the net CO producing abilities over these catalysts are also compared (Fig.…”

Double sulfur vacancies by lithium tuning enhance CO2 electroreduction to n-propanol

“…These surface sulfur atoms can be removed to form sulfur vacancies, designated as CuS x (0 < x < 1) 31 , 33 . The controlled sulfur vacancies can lower the oxidation of copper between 0 and +2, which has been proved to promote C–C coupling 34 . Herein, we developed a double-sulfur vacancy (DSV) structure using a lithium electrochemical tuning approach, which allowed for stabilization of both CO* and a *C 2 dimer (i.e., OCCO*), as well as subsequent coupling with a third *CO via CO–OCCO (Fig.…”

Copper Dimer Anchored in g‐CN Monolayer as an Efficient Electrocatalyst for CO2 Reduction Reaction: A Computational Study

“…In recent several years, Cu has attracted wide research interests, as it is the overriding inexpensive transition metal and can be capable of producing valuable multicarbon products. [ 8,10,37–39 ] In this work, Cu dimer anchored in g‐CN (Cu 2 @CN) monolayer as a promising CO 2 RR electrocatalyst is investigated and discussed in detail using density functional theory (DFT) calculations. Our computational results show that the Cu 2 @CN monolayer can electrochemically convert CO 2 to various hydrocarbons, including HCOOH and C 2 H 4 , whose excellent catalytic performance exceeds that of the corresponding single‐atom counterpart (Cu@CN).…”