Achieving Efficient CO₂ Electroreduction to Multicarbon Products by Enhancing CO Coverage With Hydrophobic Tandem...

Electrocatalytic CO₂ reduction (CO₂RR) to multicarbon (C₂₊) products is highly attractive to achieve efficient carbon recycling using renewable energies. However, the selectivity of value-added C₂₊ products on Cu catalysts is often limited by the insufficient coverage of adsorbed CO (^*CO) and the competing hydrogen evolution reaction (HER). Herein, we design a tandem catalyst layer (TCL) for flow cells, which is composed of hydrophobic nickel-nitrogen-carbon (Ni-N-C) material and electro-reduced Cu nanosheets to match the CO generation and carbon-carbon coupling process. The CO₂RR tests exhibit high partial current density of ∼338 mA cm^-2 and impressive Faradaic efficiency of ∼81% for C₂₊ products. In situ X-ray absorption fine structure and Raman spectroscopy characterizations, together with theoretical calculations, suggest that the Ni-N-C/Cu TCL substantially enriches the local CO concentration, thereby enhancing the ^*CO coverage on the Cu surface. Theoretical calculations further indicate that this elevated coverage triggers a thermodynamic transition of CO adsorption from face-centered cubic hollow sites to reactive atop sites, which significantly promotes carbon-carbon coupling between atop ^*CO and gaseous CO(g). Simultaneously, the hydrophobic nature of the TCL inhibits water diffusion, thereby suppressing the competing HER. This study provides an efficient approach for designing high-performance CO₂RR tandem catalysts toward C₂₊ products.