Sulfur-Doped g-C₃N₄ and BiPO₄ Nanorod Hybrid Architectures for Enhanced Photocatalytic Hydrogen Evolution under Visible Light Irradiation

We proposed a pathway to enhance the photocatalytic H2 evolution activity of g-C3N4 through the synergistic effect of upshifting the conduction band (CB) minimum and facilitating the separation rate of photoinduced electron–hole pairs. The S-doped g-C3N4 and BiPO4 nanorod hybrid composites were prepared by calcining the mixture of urea with 2-thiobarbituric acid and BiPO4 nanorods at elevated temperatures. The BiPO4/S-CN heterojunction exhibits an enhanced separation efficiency of photoinduced carriers by forming the interface of BiPO4 and g-C3N4; meanwhile, S doping upshifts the CB minimum of g-C3N4. The 0.1% BiPO4/S-CN composite (10 mg) exhibits an excellent hydrogen evolution rate of 11.7 μmol/h, which is 7.3 times that of g-C3N4 and 3.6 times that of S-CN. The enhanced photocatalytic activity of the BiPO4/S-CN composite is ascribed to the efficient separation due to the carrier migration from the CB of g-C3N4 to the CB of BiPO4, and a more negative conduction band of S-CN due to element doping.