Ampere‐Level Syngas Synthesis by Controllable Active Hydrogen Supply to Regulate CO 2 Reduction Depth on High‐Entropy (CuZnAlZrCe)O 2 Oxide Nanosheets

ABSTRACT Syngas synthesis via CO 2 electroreduction offers a low‐temperature carbon‐neutral route, yet with poor H 2 /CO ratio control and CH 4 byproduct. Herein, we decoupled * H generation and binding to modulate its supply and CO 2 reduction depth, steering efficient CO 2 ‐to‐syngas conversion. As a prototype, (CuZnAlZrCe)O 2 high‐entropy oxide (HEO) nanosheets (NSs) were synthesized via liquid‐phase templating and mild thermal decomposition. The multi‐cation disorder facilitates CO 2 activation and subsequent protonation into * COOH. Concurrently, HEO promotes water activation and accelerates * H generation, which in turn drives * COOH protonation into moderately‐protonated CO. Importantly, HEO weakens * H adsorption, suppressing H 2 overproduction and the formation of CH 4 , a deeply‐hydrogenated byproduct. Consequently, (CuZnAlZrCe)O 2 HEO achieves 58.2% CO Faradaic efficiency and 88.6% syngas selectivity, retaining > 80% syngas yield at ampere‐level current density. This work presents a robust high‐entropy catalyst that provides tunable syngas at industrially current densities, demonstrating a novel * H‐supply‐modulation strategy to regulate CO 2 reduction depth for efficient CO 2 ‐to‐syngas electrolysis.