Achieving Efficient CO 2 Electroreduction to Multicarbon Products by Enhancing CO Coverage With Hydrophobic Tandem Catalyst Layer

ABSTRACT Electrocatalytic CO 2 reduction (CO 2 RR) to multicarbon (C 2+ ) products is highly attractive to achieve efficient carbon recycling using renewable energies. However, the selectivity of value‐added C 2+ 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 CO 2 RR tests exhibit high partial current density of ∼338 mA cm −2 and impressive Faradaic efficiency of ∼81% for C 2+ 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 CO 2 RR tandem catalysts toward C 2+ products.