Photocatalytic synthesis of ammonia (NH3) holds significant potential compared with the Haber–Bosch process. However, the reported photocatalysts suffer from low efficiency owing to localized electron deficiency. Herein, Ru‐SA (single atoms)/HxMoO3−y hybrids with abundant of Mon+ (4<n<6) species neighboring oxygen vacancies (OV) are synthesized via a H‐spillover process. Detailed characterizations demonstrate that Ru‐SA/HxMoO3−y hybrids can quantitatively produce NH3 from N2 and H2 through the presence of dual active centers (Ru SA and Mon+). The Ru SA boost the activation and migration of H2, and Mon+ species act as the trapping sites of localized electrons and the adsorption and dissociation sites of N2, finally leading to NH3 synthesis on Mon+−OH. The NH3 generation rate is up to 4.0 mmol h−1 g−1, accompanied by an apparent quantum efficiency over 6.0 % at 650 nm.