Ni Cluster‐Decorated Single‐Atom Catalysts Achieve Near‐Unity CO2‐to‐CO Conversion with an Ultrawide Potential Window of ≈1.7 V

Abstract Developing efficient electrocatalysts for CO 2 reduction to CO within a broad potential range is meaningful for cascade application integration. In this work, hydrogen spillover is created and utilized to cultivate a proton‐rich environment via the simple thermolysis of a Ni‐doped Zn coordination polymer (Zn CPs (Ni)) to create asymmetric Ni single atoms co‐located with adjacent Ni nanoclusters on nitrogen‐doped carbon, termed as Ni NC&SA /N‐C, which expedites the hydrogenation of adsorbed CO 2 . Therefore, the sample demonstrates near‐unity CO 2 ‐to‐CO conversion efficiency under pH‐universal conditions in ultra‐wide potential windows: −0.39 to −2.05 V versus RHE with the current densities ranging from 0.1 to 1.0 A cm −2 in alkaline conditions, −0.83 to −2.40 V versus RHE from 0.1 to 0.9 A cm −2 in neutral environments, and −0.98 to −2.25 V versus RHE across 0.1 to 0.8 A cm −2 in acid conditions. Corresponding in situ measurements and density functional theory (DFT) calculations suggest that the enhanced H 2 O dissociation and more efficient hydrogen spillover on Ni NC&SA /N‐C (compared to Ni SA /N‐C) accelerate the protonation of adsorbed CO 2 to form *COOH intermediates. This work emphasizes the significant role of proton spillover in CO 2 RR, opening novel avenues for designing high‐performance catalysts applicable to various electrocatalytic processes.