Pressure-Dependent CO₂ Electroreduction to Methane over Asymmetric Cu-N₂ Single-Atom Sites

Single-atom catalysts (SACs) with unitary active sites hold great promise for realizing high selectivity toward a single product in the CO₂ electroreduction reaction (CO₂RR). However, achieving high Faradaic efficiency (FE) of multielectron products like methane on SACs is still challenging. Herein, we report a pressure-regulating strategy that achieves 83.5 ± 4% FE for the CO₂-to-CH₄ conversion on the asymmetric Cu-N₂ sites, representing one of the best CO₂-to-CH₄ performances. Elevated CO₂ pressure was demonstrated as an efficient way to inhibit the hydrogen evolution reaction via promoting the competing adsorption of reactant CO₂, regardless of the nature of the active sites. Meanwhile, the asymmetric Cu-N₂ structure could endow the Cu sites with stronger electronic coupling with *CO, thus suppressing the desorption of *CO and facilitating the following hydrogenation of *CO to *CHO. This work provides a synergetic strategy of the pressure-induced reaction environment regulating and the electronic structure modulating for selective CO₂RR toward targeted products.