Electron and proton storage on separate Ru and BaO domains mediated by conductive low-work-function carbon to accelerate ammonia synthesis

Abstract

Ammonia (NH₃) has gained attention as a carbon-free fuel and hydrogen carrier, making its energy-efficient production increasingly important. Here we demonstrate that Ru and BaO, connected by conductive carbon, can separately store e⁻ and H⁺, like a chemical capacitor under NH₃ synthesis conditions. H atoms generated on the Ru surface by H₂ activation polarize into H⁺/e⁻ pairs. Subsequently, H⁺ migrates over the carbon surfaces to neutralize basic BaO, while e⁻ accumulates in conductive Ru/carbon. As the work function of carbon decreases, Ru gradually becomes enriched with e⁻, facilitating N₂ activation via π-backdonation and alleviating H₂ poisoning. Thus, an optimized catalyst synthesized using N-doped MWNT with the lowest work function, exhibited 7.4 times higher activity than a reference Ba–Ru/MgO catalyst. The results show that charge distribution within catalysts can be markedly altered under reaction conditions, and its rational control can enable the design of active NH₃ synthesis catalysts.