Hydrogen radical-boosted electrocatalytic CO<sub>2</sub> reduction using Ni-partnered heteroatomic pairs.

Yao, Zhibo; Cheng, Hao; Xu, Yifei; Zhan, Xinyu; Hong, Song; Tan, Xinyi; Wu, Tai-Sing; Xiong, Pei et al. · Nat Commun · 2024

basic_science · Level V

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Abstract

The electrocatalytic reduction of CO<sub>2</sub> to CO is slowed by the energy cost of the hydrogenation step that yields adsorbed *COOH intermediate. Here, we report a hydrogen radical (H•)-transfer mechanism that aids this hydrogenation step, enabled by constructing Ni-partnered hetero-diatomic pairs, and thereby greatly enhancing CO<sub>2</sub>-to-CO conversion kinetics. The partner metal to the Ni (denoted as M) catalyzes the Volmer step of the water/proton reduction to generate adsorbed *H, turning to H•, which reduces CO<sub>2</sub> to carboxyl radicals (•COOH). The Ni partner then subsequently adsorbs the •COOH in an exothermic reaction, negating the usual high energy-penalty for the electrochemical hydrogenation of CO<sub>2</sub>. Tuning the H adsorption strength of the M site (with Cd, Pt, or Pd) allows for the optimization of H• formation, culminating in a markedly improved CO<sub>2</sub> reduction rate toward CO production, offering 97.1% faradaic efficiency (FE) in aqueous electrolyte and up to 100.0% FE in an ionic liquid solution.