Photocatalytic reduction of CO2 into hydrocarbon solar fuels over g-C3N4–Pt nanocomposite photocatalysts

Abstract

Photocatalytic reduction of CO₂ into renewable hydrocarbon fuels is an alternative way to develop reproducible energy, which is also a promising way to solve the problem of the greenhouse effect. In this work, graphitic carbon nitride (g-C₃N₄) was synthesized by directly heating thiourea at 550 °C and then a certain amount of Pt was deposited on it to form g-C₃N₄–Pt nanocomposites used as catalysts for photocatalytic reduction of CO₂ under simulated solar irradiation. The main products of photocatalysis were CH₄, CH₃OH and HCHO. The deposited Pt acted as an effective cocatalyst, which not only influenced the selectivity of the product generation, but also affected the activity of the reaction. The yield of CH₄ first increased upon increasing the amount of Pt deposited on the g-C₃N₄ from 0 to 1 wt%, then decreased at 2 wt% Pt loading. The production rates of CH₃OH and HCHO also increased with the content of Pt increasing from 0 to 0.75 wt% and the maximum yield was observed at 0.75 wt%. The Pt nanoparticles (NPs) could facilitate the transfer and enrichment of photogenerated electrons from g-C₃N₄ to its surface for photocatalytic reduction of CO₂. At the same time, Pt was also used a catalyst to promote the oxidation of products. The transient photocurrent response further confirmed the proposed photocatalytic reduction mechanism of CO₂. This work indicates that the deposition of Pt is a good strategy to improve the photoactivity and selectivity of g-C₃N₄ for CO₂ reduction.