Facile synthesis of sulfur-doped Ni(OH)2 as an efficient co-catalyst for g-C3N4 in photocatalytic hydrogen evolution

In this study, sulfur-doped Ni(OH) 2 was prepared by an immersion method at room temperature and used as an efficient co-catalyst for g-C 3 N 4 in photocatalytic hydrogen evolution . The structure, morphology, and elemental composition of the sulfur-doped Ni(OH) 2 /g-C 3 N 4 were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy , and X-ray photoelectron spectroscopy. These results proved that the sulfur-doped Ni(OH) 2 was successfully synthesized and combined with g-C 3 N 4 at the heterojunction . The photocatalytic hydrogen generation results of Ni(OH) 2 /g-C 3 N 4 (0 μmol g −1  h −1 ) and that of sulfur-doped Ni(OH) 2 /g-C 3 N 4 (1573.7 μmol g −1  h −1 ) indicate that the sulfur doping resulted in significant improvement in the catalytic activity of co-catalyst Ni(OH) 2 . Moreover, the possible mechanism of photocatalytic hydrogen evolution catalyzed by the sulfur-doped Ni(OH) 2 /g-C 3 N 4 was proposed. The results of photoluminescence , ultraviolet–visible diffuse reflectance spectroscopy , and electrochemical analysis demonstrated that the sulfur doping provided more active sites in Ni(OH) 2 , leading to the efficient hydrogen evolution reaction, thus indirectly enhancing the separation efficiency of electron–hole pairs and the migration efficiency of photogenerated electrons by the photocatalyst g-C 3 N 4 .