Ammonia holds crucial and widespread applications in modern agriculture and various industrial production sectors. The traditional Haber process directly converts hydrogen and nitrogen gases into ammonia, which consumes an enormous amount of energy while bringing about serious environmental pollution. In contrast, electrocatalysis boasts prominent advantages such as mild reaction conditions, high selectivity, and environmental friendliness, thus making it a major research hotspot in the field. Among them, the rational development of low-cost catalysts for the efficient and highly selective synthesis of ammonia remains the core key to this technology. In this study, waste corn stalks were used as a carbon source and phytic acid as a phosphorus source to successfully prepare a biomass carbon-supported iron-nickel bimetallic phosphide catalyst (NiFeP/PBC) using a one-step calcination method. The catalyst exhibited excellent electrocatalytic nitrite reduction (eNO₂RR) performance for ammonia synthesis, at a voltage of -0.2 V vs. RHE, the faradaic efficiency reaches as high as 95.9%, the ammonia yield achieves 304.9 μmol·h^-1·cm^-2, and the catalyst exhibits excellent stability (over 15 cycling tests). Electrochemical in-situ infrared studies indicated that key intermediates such as NO, NH₂, and NH₃ were generated during the reaction, and active hydrogen (*H) played an important role in the reduction process. Both XRD and SEM characterizations demonstrated that the morphology of the catalyst did not change significantly after the reaction, and ¹⁵N isotope labeling experiments confirmed that all nitrogen in the solution originated from the electrolyte rather than the environment. Meanwhile, the tests revealed that the catalyst possessed a larger electrochemical active surface area and more prominent ammonia production performance in the presence of a phosphorus source, confirming that the introduction of phosphorus can optimize the water dissociation process and hydrogen adsorption energy. This study offers a new strategy for waste biomass valorization and green electrochemical ammonia synthesis, with great scientific significance and application potential for developing high-efficiency, low-cost electrocatalysts and preparing carbon-supported metal materials from renewable energy production.

Key words: NiFeP/PBC, biomass, nitrite reduction, electrocatalytic ammonia synthesis