Photocatalytic　ammonia　synthesis　is　of　great　importance　but　remains　very　challenging　in　photocatalysis.　Here,　we　fabricated　a　photocatalytic　reaction　system　for　the　efficiently　photocatalytic　nitrate　reduction　to　ammonia　under　UV　irradiation　using　PdSniNiO/NaTaO3:La　as　a　photocatalyst　in　the　presence　of　formic　acid.　Several　important　factors　of　the　photocatalytic　performance　were　investigated,　including　initial　concentration　of　the　nitrate　solution,　initial　pH　value　and　cocatalyst　loadings.　Nitrate　conversion　reaches　100%　and　ammonia　selectivity　is　72%　over　the　optimum　photocatalyst　with　5%　bimetallic　PdSn　alloy　and　0.2%　NiO　loadings.　The　outstanding　performance　of　photocatalyst　can　be　ascribed　to　both　the　strong　adsorption　of　nitrite　on　NiO　and　the　efficient　separation　of　electron-hole　pairs　by　PdSn　bimetallic　alloy.　Besides　as　the　hole　scavenger,　formic　acid　also　provides　not　only　carboxyl　anion　radicals　for　nitrate　reduction　but　also　the　in-situ　buffer　effect　on　ammonia　formation.　These　results　give　inspiration　for　designing　the　reactive　system　with　efficient　photocatalytic　ammonia　synthesis.　(C)　2018　Elsevier　Inc.　All　rights　reserved.