Efficient photocatalytic hydrogen evolution with end-group-functionalized cobaloxime catalysts in combination with graphite-like C3N4

Abstract

Three comparable hybrid photocatalytic systems, comprising semiconductor g-C₃N₄, end-group-functionalized cobaloxime complexes (carboxy-functionalized cobaloxime, C1; pyrene-functionalized cobaloxime, C2; and non-functionalized cobaloxime, C3), and triethanolamine (TEOA), are active for visible-light-driven hydrogen production in CH₃CN–H₂O (9/1, v/v) solution. Upon irradiation for 12 h, the turnover numbers of hydrogen evolution are 234, 281 and 195 for the hybrid systems C1/g-C₃N₄, C2/g-C₃N₄ and C3/g-C₃N₄, respectively. The highest hydrogen evolution efficiency of the C2/g-C₃N₄ system can be attributed to the strongest π–π interactions between the pyrene moiety and g-C₃N₄. Based on electrochemical properties, steady-state photoluminescence spectra and theoretical analyses, the visible light absorption of g-C₃N₄, the catalytic H₂-evolving ability of cobaloxime as well as the efficient charge separation of the excited g-C₃N₄ in the presence of both TEOA and cobaloxime, are responsible for the high activity of these hybrid systems.