Optimizing Surface * H Coverage over Cu 2 O/Co 3 O 4 Heterojunction Enables Efficient Neutral Electrocatalytic Hydrogenation of 5‐hydroxymethylfurfural to 2,5‐dihydroxymethylfuran

Abstract Electrochemical hydrogenation (ECH) of biomass‐derived 5‐hydroxymethylfurfural (HMF) to 2,5‐dihydroxymethylfuran (DHMF) offers a sustainable route for biomass valorization. Recent studies have underscored the importance of reactive hydrogen species ( * H) on the catalyst surface in determining reaction selectivity, particularly under neutral conditions. However, the mechanistic understanding of how * H coverage governs the reaction pathway remains poorly understood, and effective strategies for optimizing surface * H coverage are still lacking. Herein, density functional theory (DFT) calculations first reveal that an optimum * H coverage on the Cu 2 O surface effectively suppresses ketyl intermediate coupling and thermodynamically favors DHMF formation. Inspired by this insight, a Cu 2 O/Co 3 O 4 heterojunction catalyst is constructed, in which Co 3 O 4 serves as a redox‐active cocatalyst to stabilize Cu⁺ sites and modulate the electronic structure of Cu 2 O, thereby enhancing H 2 O activation and enabling precise tuning of * H coverage. The Cu 2 O/Co 3 O 4 heterojunction catalyst delivers an excellent HMF conversion (97%) and DHMF selectivity (97%), significantly outperforming the pristine Cu 2 O (71% DHMF selectivity, 62% HMF conversion). This work uncovers the mechanistic role of * H coverage in pathway regulation and highlights heterointerface engineering as a powerful strategy for designing efficient electrocatalysts for selective biomass upgrading under neutral conditions.