Embedding Pure-Phase Fe3C Functional Sites Into Biochar Matrix for Multi-Scenario Electrocatalytic Ammonia Synthesis and Energy Conversion Utilization

Abstract

The rational design and development of application-oriented advanced functional catalysts is crucial for facilitating the conversion of nitrogen oxides into high-value ammonia. Herein, biomass derived from the pomelo peel, which is rich in metal complex groups and exhibits a metallic foam-like framework, is utilized as a precursor. Iron carbide (Fe₃C) active sites are incorporated into the locally 2D, and globally 3D biochar structure, enabling the multi-scenario green synthesis of ammonia and integrated energy utilization. As a catalyst, Fe₃C-BC achieved an ammonia yield rate of up to 102120.53 µg h⁻¹ mg_cat⁻¹, with a maximum ammonia selectivity of 100%. A flow-based electrolysis system featuring Fe₃C-BC not only facilitated the continuous synthesis of ammonia but also enhanced solar energy harvesting. Additionally, a nitrate battery employing Fe₃C-BC as the anode exhibited high energy output and enabled self-driven ammonia synthesis, offering novel insights and operational solutions for the future of green ammonia production. Density-functional-theory calculations confirmed that Fe₃C actively reduces the energy barrier of key steps in the eNitRR process while accelerating water dissociation to promote sustained proton supply. These findings collectively provide a promising foundation for advancing the green synthesis of ammonia, emphasizing both efficient catalytic performance and sustainable energy integration.