Porous　Ni2+-doped　Co3O4　nanosheets　were　prepared　by　a　combination　method　of　electrodeposition　and　postcalcination.　The　catalytic　activities　of　the　as-prepared　samples　for　the　electrocatalytic　nitrate　reduction　to　ammonia　were　evaluated.　It　was　found　that　the　Ni2+-doped　Co3O4　sample　with　a　Ni2+　doping　content　of　20　%　exhibited　higher　catalytic　activity　as　compared　with　other　samples.　The　outstanding　catalytic　activity　of　the　20　%　Ni2+-doped　Co3O4　sample　could　be　attributed　to　its　porous　nanosheet　structure　with　rich　oxygen　vacancies,　which　was　confirmed　by　SEM,　XPS,　TEM,　EPR　and　operando　EIS　analyses.　The　DFT　results　further　revealed　that　the　increased　hydrogen　generation　energy　and　nitrate　adsorption,　and　the　diminished　rate-determining　step　energy　barrier　ensured　Ni2+-doped　Co3O4　exhibited　outstanding　activity　for　the　electrocatalytic　nitrate　reduction.　Moreover,　membrane-less　electrocatalytic　nitrate　reduction　was　coupled　with　methanol　oxidation　by　using　the　oxygen　vacancies-rich　Co3O4　electrocatalyst.　The　Faradic　efficiencies　for　the　electroreduction　of　nitrate　to　ammonia　and　the　electrooxidation　of　methanol　to　formate　could　keep　at　98　%　and　99　%　after　multiple　cycles,　respectively,　revealing　a　good　stability　of　the　reported　hybrid　system　for　the　membrane-less　electrocatalytic　ammonia　synthesis.