Fe<sub>3</sub>O<sub>4</sub> Nanoparticles Anchored\non Biomass Carbon as Electrocatalysts for Nitrate Reduction

The electrocatalysis of nitrate to value-added ammonia\nis an important\nstrategy to address the increasingly pressing problem of nitrate pollution.\nNonetheless, this remains a challenging topic within the field of\ncatalysis. Iron-based materials are considered promising catalysts\nfor the reduction of nitrate to NH<sub>3</sub>, but they are prone\nto agglomeration, with low yields and Faraday efficiencies. In this\nstudy, Fe<sub>3</sub>O<sub>4</sub> nanoparticles were anchored to\nbiomass carbon (BC) through in situ annealing strategy, which can\nutilize the reducing properties of BC to convert Fe<sup>3+</sup> ions.\nThese findings indicate that by modulating the annealing temperature\nwith BC, the ratio of Fe<sup>3+</sup> to Fe<sup>2+</sup> on the catalyst\nsurface can be adjusted, thereby increasing the active sites available\non the catalyst for promoting nitrate reduction. Transient photovoltage\nspectroscopy also indicated that the introduction of BC contributed\nto the increase of electron transfer rate. The Faraday efficiency\nof the Fe<sub>3</sub>O<sub>4</sub>/BC-700 catalyst for NH<sub>3</sub> in the presence of 100 mM NO<sub>3</sub><sup>–</sup> at −0.5\nV vs RHE was 91.10% (±2.36) with a yield rate of 4274.25 (±110.09)\nmmol g<sub>cat</sub><sup>–1</sup> h<sup>–1</sup>. The\nresults pave the way for sustainable ammonium synthesis using low-cost\nand environmentally friendly materials with improved catalytic properties\nby adjusting the surface structure and interface behavior.