Fe₃O₄ Nanoparticles Anchored on Biomass Carbon as Electrocatalysts for Nitrate Reduction

The electrocatalysis of nitrate to value-added ammonia is an important strategy to address the increasingly pressing problem of nitrate pollution. Nonetheless, this remains a challenging topic within the field of catalysis. Iron-based materials are considered promising catalysts for the reduction of nitrate to NH3, but they are prone to agglomeration, with low yields and Faraday efficiencies. In this study, Fe3O4 nanoparticles were anchored to biomass carbon (BC) through in situ annealing strategy, which can utilize the reducing properties of BC to convert Fe3+ ions. These findings indicate that by modulating the annealing temperature with BC, the ratio of Fe3+ to Fe2+ on the catalyst surface can be adjusted, thereby increasing the active sites available on the catalyst for promoting nitrate reduction. Transient photovoltage spectroscopy also indicated that the introduction of BC contributed to the increase of electron transfer rate. The Faraday efficiency of the Fe3O4/BC-700 catalyst for NH3 in the presence of 100 mM NO3– at −0.5 V vs RHE was 91.10% (±2.36) with a yield rate of 4274.25 (±110.09) mmol gcat–1 h–1. The results pave the way for sustainable ammonium synthesis using low-cost and environmentally friendly materials with improved catalytic properties by adjusting the surface structure and interface behavior.