Ultrasmall Nickel Nanoclusters Accelerating Protonation for Efficient CO <sub>2</sub> Electroreduction towards CO
Jun Wu, Wuyi Zhang, Lin Wu, Xinlei Wang, Jing Yuan, Kailong Xu, Yani Hua, Zhan Gao, Hui Liu, Min Liu
Abstract
Abstract Proton‐coupled electron transfer (PCET), particularly the protonation step is widely recognized as the kinetic bottleneck in electrochemical CO 2 reduction (CO 2 RR). Modulating catalyst microstructures to accelerate protonation has thus emerged as a promising strategy to boost from CO 2 to CO selectivity. Here, we report ultrasmall Ni nanocluster catalysts (denoted as Ni 3 ─N─C) prepared via one‐step pyrolysis of Ni‐containing precursors under H 2 atmosphere. Compared to conventional Ni─N─C with symmetric Ni─N 4 motifs, Ni 3 ─N─C displays similar physicochemical characteristics—Ni loading, defect density, surface area—yet exhibits distinct local Ni coordination environments. These sub‐nanoclusters markedly enhance CO 2 RR performance, delivering > 90% CO Faradaic efficiency (FE CO ) across −0.6 to −1.0 V versus RHE, with a peak FE CO of ∼95% at −0.8 V. Density functional theory calculations reveal that Ni 3 ─N─C substantially lowers the energy barrier for *COOH formation owing to altered adsorption configurations, thereby facilitating the rate‐limiting protonation step. In situ FTIR measurements further confirm the accelerated *COOH formation on Ni 3 ─N─C surfaces. This work highlights the critical role of Ni sub‐nanoclusters in PCET modulation and establishes a rational design principle for nanocluster‐based catalysts in CO 2 RR.