Exfoliated g-C₃N₄–MoO₃–Fe₃O₄ hybrids enabling selective and electrochemical ammonia synthesis

Electrochemical nitrogen reduction (eNRR) offers a carbon-free route to ammonia under ambient conditions but remains limited by inefficient N₂ activation and severe competition from the hydrogen evolution reaction (HER). Here we develop a hierarchical nCN–MoO₃–Fe₃O₄ electrocatalyst by integrating exfoliated nitrogen-rich carbon nitride nanosheets with Mo/Fe oxides on carbon cloth. The exfoliated support enhances dispersion and interfacial coupling of the oxide domains and modulates electronic structure to promote N₂ adsorption and activation while suppressing H* binding. In 0.1 M phosphate buffer, the optimized catalyst achieves an NH₃ yield of 23.56 μg h⁻¹ mg⁻¹ and a Faradaic efficiency of 21.77% at −0.20 V vs RHE, outperforming bulk carbon nitride and oxide-only controls. Electrolyte and potential screening identify phosphate buffer as the most effective medium, and the catalyst exhibits sustains stable performance during prolonged electrolysis. XPS indicates dynamic evolution of nitrogen environments together with Mo/Fe redox changes during eNRR, while DFT calculations reveal reduced free-energy barriers along the distal pathway and suppressed HER on the nCN-stabilized heterointerface. This work highlights an interface-engineering strategy for selective and durable ammonia electrosynthesis using carbon nitride/metal-oxide hybrids.