Revealing the Kinetic Balance between Proton‐Feeding and Hydrogenation in CO2 Electroreduction

Electrocatalytic reduction of CO2 to high‐value‐added chemicals provides a feasible path for global carbon balance. Herein, the fabrication of NiNPx@NiSAy‐NG (x,y = 1, 2, 3; NG = nitrogen‐doped graphite) is reported, in which Ni single atom sites (NiSA) and Ni nanoparticles (NiNP) coexist. These NiNPx@NiSAy‐NG presented a volcano‐like trend for maximum CO Faradaic efficiency (FECO) with the highest point at NiNP2@NiSA2‐NG in CO2RR. NiNP2@NiSA2‐NG exhibited ≈98% of maximum FECO and a large current density of −264 mA cm−2 at −0.98 V (vs. RHE) in the flow cell. In situ experiment and density functional theory (DFT) calculations confirmed that the proper content of NiSA and NiNP balanced kinetic between proton‐feeding and CO2 hydrogenation. The NiNP in NiNP2@NiSA2‐NG promoted the formation of H* and reduced the energy barrier of *CO2 hydrogenation to *COOH, and CO desorption can be efficiently facilitated by NiSA sites, thereby resulting in enhanced CO2RR performance. It is reported that the kinetic balance between proton‐feeding and hydrogenation in CO2 electroreduction by fine‐tuning the content of Ni single atom sites and Ni nanoparticles (denoted as NiNPx@NiSAy‐NG (x,y = 1,2,3)). As a result, CO Faraday efficiency of 98% at −0.58 V (vs. RHE) and the current density of −264 mA cm−2 at −0.98 V (vs. RHE) can be achieved in NiNP2@NiSA‐NG.