Fabrication of Heterostructured g-C3N4/Ag-TiO2 Hybrid Photocatalyst with Enhanced Performance in Photocatalytic Conversion of CO2 Under Simulated Sunlight Irradiation

Abstract

Heterostructured g-C3N4/Ag-TiO2 (CN/AgTi) hybrid catalysts were fabricated through a facile solvent evaporation followed by a calcination process, using graphitic carbon nitride (g-C3N4) and Ag-TiO2 (AgTi) as precursors. The phase compositions, optical properties, and morphologies of the catalysts were systematically characterized. The heterostructured combination of g-C3N4, titania (TiO2) and silver nanoparticles (Ag NPs) resulted in significant synergy for catalytic conversion of CO2 in the presence of water vapor under simulated sunlight irradiation. The optimal CN/AgTi composite with a g-C3N4 to AgTi mass ratio of 8% exhibited the maximum CO2 photoreduction activity, achieving a CO2 conversion of 47μmol, CH4 yield of 28μmol, and CO yield of 19μmol per gram of catalyst during a 3h simulated sunlight irradiation. Under the experimental conditions, the rate of electron consumption was calculated to be 87.3μmol/g·h, which was 12.7 times, 7.9 times, and 2.0 times higher than those for TiO2, g-C3N4 and AgTi, respectively. The combination of g-C3N4 and AgTi resulted in more sunlight harvesting for electron and hole generations. Photoinduced electrons transferred through the heterjunction between g-C3N4 and TiO2, and further from TiO2 to Ag NPs with lower Fermi level greatly suppressed the recombination of electron-hole pairs, and hence resulted in electron accumulation on Ag NPs deposited on the TiO2 surface in the CN/AgTi. Abundant electrons accumulated on the Ag NPs were further energized by the surface plasmon resonance effect with the aid of visible light. Therefore, the CN/AgTi catalysts exhibited superior catalytic performance in CO2 reduction by water vapor under simulated sunlight irradiation.