Abstract For metal sulfide photocatalysts, the excellent antiphotocorrosion and high hydrogen-production activity are highly required during light irradiation. Herein, an effective route of the direct addition of cobalt nitrate into lactic acid (LA) sacrificial agent solution was applied to greatly boost the antiphotocorrosion and H2-production activity of the well-known CdS system. It was found that the introduction of cobalt nitrate into the LA solution causes the rapid production of stable [Co(LA)2(H2O)2]3+/2+ complex, which cannot be deposited on the CdS surface during H2-production progress. In this case, the produced [Co(LA)2(H2O)2]3+/2+ not only exhibits an apparently higher H2-evolution rate of CdS nanoparticles but also can maintain their excellent photocorrosion resistance, even after the further photodeposition of metallic Au cocatalyst on the CdS surface. Therefore, the hydrogen-production activity of CdS/Au-Co can reach 86.46 μmol h−1, which is as high as that of CdS, CdS/Au and CdS-Co by the factor of 10.16, 1.99 and 2.29 times, respectively. An interesting [Co(LA)2(H2O)2]3+/2+-mediated photocatalytic mechanism was proposed to account the simultaneously boosted antiphotocorrosion and H2-production activity of the CdS photocatalysts. The present facile route about the direct addition of transition-metal ions can be considered as a general strategy for CdS photocatalysts in LA sacrificial agent system.