Evidence for plasmonic hot electron injection induced superior visible light photocatalysis by g-C3N4 nanosheets decorated with Ag–TiO2(B) and Au–TiO2(B) nanorods

Abstract

Hot electrons produced by the surface plasmon decay can be efficiently utilized to drive photochemical reactions on a semiconductor surface. Considering this aspect of plasmonics, we have evaluated the visible light photocatalytic performance of Ag–TiO2(B)–C3N4 and Au–TiO2(B)–C3N4 heterostructures in the degradation of rhodamine B (RhB) and phenol. The synergetic effect of plasmonic hot electron injection and interfacial charge transfer in the heterostructures lead to 6–9 fold enhancement in the photodecomposition rate of RhB (phenol) over TiO2(B) and C3N4. Time-resolved photoluminescence study shows fast charge transfer through the integrated network of the heterostructure. The photocurrent is measured at 470 nm, 510 nm and 575 nm, near the plasmonic excitations of Ag and Au as well as under white light illumination (400–800 nm). Plasmonic systems show more than 6-fold enhancement in photocurrent over bare TiO2(B) under illumination near monochromatic plasmonic excitation. The overall photocurrent resulting from white light illumination is 2-fold stronger than that under plasmonic excitation. The increase is due to the contribution from Ti3+ excitation, hot electron injection, and charge transfer from TiO2(B) to C3N4. We propose that Ti3+ states in TiO2(B) provide channels for direct hot electron transfer from metal to semiconductor facilitating charge separation for participation in photocatalysis.