Gradient Doping of Tandem Catalysts to Boost Ethanol Production at Low Potential during CO2 Electroreduction

The electrochemical reduction of carbon dioxide (CO2ER) to valuable C2+ chemicals has been demonstrated to be an effective and sustainable method using Cu-based catalysts. However, Cu catalysts still suffer from certain limitations, including high overpotential, low selectivity, and competitive hydrogen evolution. To achieve the valuable ethanol (C2H5OH) product from the CO2ER, a novel tandem catalyst featuring gradient doping of Cu in concave Pd nanoparticles (GD-PdCu1.8 NPs) was designed in this study. Electrochemical tests conducted on the GD-PdCu1.8 electrode reveal a nearly 100% faradaic efficiency (FE) for liquid products and a high FE of 40.0% for C2H5OH at the extremely low potential of −0.2 V versus the reversible hydrogen electrode (vs RHE). Furthermore, in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and density functional theory (DFT) calculations provide insights into the underlying mechanism, indicating that gradient Cu doping in Pd can effectively facilitate the abundant formation of *CO, which then promotes the C–C asymmetric coupling step and ultimately leads to the production of C2H5OH with high selectivity. This study unveils the novel gradient doping of the tandem catalyst strategy to enhance multicarbon product selectivity at a relatively low overpotential for CO2ER, which can inform the rational catalyst design in the sustainable carbon cycle with high energy efficiency.