Sulfur-Doped g-C₃N₄/BiVO₄ Composite Photocatalyst for Water Oxidation under Visible Light

Abstract

To achieve sustainable utilization of solar energy, development of an efficient photocatalyst for water oxidation, the driving force of reductive solar fuel formation, is strongly needed. Herein, composite photocatalysts with bismuth vanadate (BiVO4) and sulfur-doped graphitic carbon nitride (SCN) are developed by using a one-pot impregnated precipitation method. Fourier transform infrared and X-ray photoelectron spectroscopy analyses demonstrate that the surface of SCN is oxidized during impregnation and the oxidized surface becomes the synthetic site for BiVO4 composition. Among the composites with various ratios, the B7S catalyst, which is our best achievement, shows an oxygen evolution rate of 750 μmol h–1 g–1 that is >2-fold higher than that of pristine BiVO4 (i.e., 328 μmol h–1 g–1) under identical reaction conditions [0.05 M AgNO3 aqueous solution under visible light irradiation (λ > 420 nm)]. The photonic efficiency of B7S is also measured as 19%. The mechanism behind this is the enhanced charge carrier lifetime of B7S (3.14 ns), which is lengthened up to 4 times compared to that of BiVO4 (0.70 ns) because of the facilitated charge separation through the composite.