《Angew. Chem. Int. Ed.》: Ampere-Level Syngas Synthesis by Controllable Active Hydrogen Supply to Regulate CO₂ Reduction Depth on High-Entropy (CuZnAlZrCe)O₂ Oxide Nanosheets

Peipei Li,⁺ Wenya Fan,⁺ Haochen Zhang,⁺ Changjing Wang, Mengqian Li, Zequn Han, Liang Chen,* Xingchen Jiao,* and Qingxia Chen*

Syngas synthesis via CO₂ electroreduction offers a low-temperature carbon-neutral route, yet with poor H₂/CO ratio controland CH₄ byproduct. Herein, we decoupled *H generation and binding to modulate its supply and CO₂ reduction depth,steering efficient CO₂-to-syngas conversion. As a prototype, (CuZnAlZrCe)O₂ high-entropy oxide (HEO) nanosheets (NSs) weresynthesized via liquid-phase templating and mild thermal decomposition. The multi-cation disorder facilitates CO₂ activationand subsequent protonation into * COOH. Concurrently, HEO promotes water activation and accelerates *H generation, whichin turn drives *COOH protonation into moderately-protonated CO. Importantly, HEO weakens *H adsorption, suppressing H₂ overproduction and the formation of CH₄ , a deeply-hydrogenated byproduct. Consequently, (CuZnAlZrCe)O₂ HEO achieves58.2% CO Faradaic efficiency and 88.6% syngas selectivity, retaining > 80% syngas yield at ampere-level current density. Thiswork presents a robust high-entropy catalyst that provides tunable syngas at industrially current densities, demonstrating a novel *H-supply-modulation strategy to regulate CO₂ reduction depth for efficient CO₂-to-syngas electrolysis.