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

Developing efficient electrocatalysts for CO 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/N-C, which expedites the hydrogenation of adsorbed CO. Therefore, the sample demonstrates near-unity CO-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 in alkaline conditions, -0.83 to -2.40 V versus RHE from 0.1 to 0.9 A cm in neutral environments, and -0.98 to -2.25 V versus RHE across 0.1 to 0.8 A cm in acid conditions. Corresponding in situ measurements and density functional theory (DFT) calculations suggest that the enhanced HO dissociation and more efficient hydrogen spillover on Ni/N-C (compared to Ni/N-C) accelerate the protonation of adsorbed CO to form *COOH intermediates. This work emphasizes the significant role of proton spillover in CORR, opening novel avenues for designing high-performance catalysts applicable to various electrocatalytic processes.