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Two bipyridyl-iridium(III) complexes as catalysts for visible light driven hydrogen production in the buffer solution of ascorbic acid/sodium ascorbate (H 2 A/NaHA) were studied. Proton and H 2 O coordination to complex in aqueous solution and the release of H 2 from the hydride species occurred by a direct reaction with protons. These two complexes could demonstrate the emergence of hydrides by electrochemical methods in the case of water or protons. [Display omitted] • Two bipyridyl-iridium(III) complexes were used as catalysts for visible light driven hydrogen production. • These complexes could electrochemically prove the appearance of hydrides in the presence of water or weak acids. • The hydrides obtained by electrolysis could exist stably for a period of time, which had been proved by 1H NMR spectra. In this article, we mainly discussed that iridium(III) complexes [IrIII(L) 2 Cl 2 ]PF 6 (L = 4,4′-dimethyl-2,2′-bipyridine or 4,4′-di- tert -butyl-2,2′-bipyridine) could be used as homogeneous catalysts to catalyze aqueous solutions in the presence of photosensitizers and electronic victims. The appearance of hydrides was the key to hydrogen production. In order to conduct a more thorough study of these species, here the catalysts were electrolyzed in CH 3 CN to continuously obtain electrons. At the same time, the presence of weak acid (n Bu 4 NH 2 PO 4) introduced hydrogen ions, so that iridium hydride can be continuously produced. Then UV–vis absorption and NMR spectroscopies were used to characterize the hydride. [ABSTRACT FROM AUTHOR]