Preserving Cu⁺ Active Sites through Intensified Electron Density for Sustained CO₂ Electroreduction

In the realm of CO2 electroreduction to C-2 fuels and feedstocks, copper-based oxides (CuOx) stand out for their exceptional ability to adsorb *CO intermediates. A significant challenge in the use of Cu-based oxide catalysts is the electroreduction-driven transformation of Cu+ species to metallic Cu, predominantly attributed to the direct electron-mediated disruption of Cu-O bonds. Addressing this, our study introduces an approach that enhances the electron density in Cu2O through the integration of MoS2, thereby stabilizing the Cu+ species. This method mitigates the Cu-O bond attack by dispersing the excess electrons, which originate from the external electrode, within the Cu2O. Our composite material, Cu2O-MoS2, demonstrates a 1.9-fold increase in Faraday efficiency for C2H4 production (FEC2H4), achieving 23.3% at -1.3 V vs RHE, and exhibits predominant Cu+ stability compared to pure Cu2O. Both experimental and computational analyses reveal that the lower work function (WF) of MoS2, relative to Cu2O, facilitates electron transfer from MoS2 to Cu2O, consequently augmenting the electron density in Cu2O. This increased electron density provides a protective barrier against electron attacks from the external electrode on the Cu-O bond. Our findings present a strategy for enhancing Cu+ stability, thereby promoting C2H4 production. Furthermore, this research contributes a different insight into the design of selective and stable catalysts for CO2 reduction.