Dynamic Cr-valence regulation and interfacial electronic reconstruction in hierarchical Cr2O3@CuO heterostructures for high-efficiency ammonia-to-hydrogen conversion

As ammonia (NH 3 ) emerges as a pivotal renewable hydrogen carrier, the development of cost-effective and high-performance electrocatalysts for the ammonia oxidation reaction (AOR) is imperative for sustainable hydrogen production. However, non-noble-metal catalysts are frequently bottlenecked by sluggish kinetics, restricted active-site exposure, and severe intermediate poisoning. Herein, a hierarchical Cr 2 O 3 @CuO heterostructure was synthesized on nickel foam via a two-step hydrothermal method. The optimized nanocatalyst delivers a remarkable AOR activity, achieving 10 mA cm −2 at a low potential of 1.32 V vs. RHE, alongside exceptional durability for 36 h at a high current density of 150 mA cm −2 . Experimental and density functional theory (DFT) studies reveal that Cr incorporation enriches oxygen vacancies and downshifts the d-band center from −1.12 eV to −1.79 eV. Notably, the dynamic evolution of high-valent Cr 6+ species during AOR effectively attenuates intermediate adsorption, lowering the maximum dehydrogenation free-energy barrier from 2.06 to 0.96 eV. This study underscores the significance of dynamic valence regulation in enhancing AOR kinetics and provides a robust paradigm for the rational design of transition-metal-based catalysts for the ammonia-to-hydrogen economy.