Tailoring the Catalytic Microenvironment of large-scale Cu foil with Polyaniline to Enhance CH4 Selectivity in CO2 Electroreduction

Abstract

Electrochemical conversion of CO2 into liquid fuels and value-added chemicals is a promising approach to close the carbon cycle. Copper (Cu) is considered as one of the most effective catalysts for electrocatalytic CO2 reduction reaction (CO2RR). However, its utilization potentiality is limited by poor selectivity for hydrocarbon products and the competing hydrogen evolution reaction (HER). In this study, we present a strategy to suppress the HER process and enhance the CH4 selectivity of large-scale Cu foil toward CO2RR. By coating the Cu foil surface with a porous polyaniline (PANI) layer, the H2 Faradaic efficiency (FE) reduces from 60% to 18%. Moreover, the FE of hydrocarbons increases dramatically from 25% to 80%, and the FE of dominant product CH4 is high up to 62%. The in situ electrochemical attenuated total reflection Fourier transform infrared spectroscopy (in situ ATR-FTIR) and density functional theory (DFT) calculations are conducted to elucidate the mechanism. The enhanced performance of Cu-PANI in CO2RR is mainly attributed to the porous PANI layer, which facilitates CO2 adsorption and mass transport. This leads to a reversal in the energy barrier for the rate-determining steps between HER and CO2RR, significantly inhibiting HER and enhancing CO2RR activity. Additionally, Cu-PANI promotes the hydrogenation of *CO to *CHO, resulting in higher methane selectivity. This work provides a promising strategy for designing efficient large-scale Cu-based catalysts with high CH4 catalytic activity and selectivity.