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.