Visible-light-driven　N2　reduction　into　NH3　in　pure　H2O　provides　an　energy-saving　alternative　to　the　Haber–Bosch　process　for　ammonia　synthesizing.　However,　the　thermodynamic　stability　of　N≡N　and　low　water　solubility　of　N2　remain　the　key　bottlenecks.　Here,　we　propose　a　solution　by　developing　a　WO3−x　hollow　sphere　with　oxygen　vacancies.　Experimental　analysis　reveals　that　the　hollow　sphere　structure　greatly　promotes　the　enrichment　of　N2　molecules　in　the　inner　cavity　and　facilitates　the　chemisorption　of　N2　onto　WO3−x-HS.　The　outer　layer’s　thin　shell　facilitates　the　photogenerated　charge　transfer　and　the　full　exposure　of　O　vacancies　as　active　sites.　O　vacancies　exposed　on　the　surface　accelerate　the　activation　of　N≡N　triple　bonds.　As　such,　the　optimized　catalyst　shows　a　NH3　generation　rate　of　140.08　μmol　g−1　h−1,　which　is　7.94　times　higher　than　the　counterpart　WO3-bulk.　©　2023　by　the　authors.