Ampere-Level Syngas Synthesis by Controllable Active Hydrogen Supply to Regulate CO₂ Reduction Depth on High-Entropy...

Syngas synthesis via CO₂ electroreduction offers a low-temperature carbon-neutral route, yet with poor H₂/CO ratio control and 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) were synthesized via liquid-phase templating and mild thermal decomposition. The multi-cation disorder facilitates CO₂ 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 H₂ overproduction and the formation of CH₄, a deeply-hydrogenated byproduct. Consequently, (CuZnAlZrCe)O₂ 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 CO₂ reduction depth for efficient CO₂-to-syngas electrolysis.