Preparation And Photocatalytic CO₂ Reduction Performance Of Carbon Nitride/metal Chalcogenides

At present,serious environmental pollution accompanied by a sustained energy crisis has triggered considerable concern about the conversion of solar energy to fuels.Carbon dioxide(CO₂),as the main greenhouse gas,has been expected to be converted into chemical fuels to address the energy crisis and climate deterioration by photocatalysis technology under sunlight irradiation.Graphitic carbon nitride(g-C₃N₄)has been proved to be a promising photocatalyst due to its suitable band gap and energy band structure,good visible light response,non-toxic,non-polluting,easy to prepare,great thermal and chemical stability.Constructing g-C₃N₄heterostructures by coupling g-C₃N₄with other semiconductors with a appropriate bandgap is also one pivotal approach to improve the performance of photocatalysts.The main contents are as follows:(1)Design and synthesis of g-C₃N₄porous nanosheets embedded with ZnO-ZnSe(C₃N₄/ZnO-ZnSe).The g-C₃N₄precursor was added to the ethanol solution containing Zn²⁺for dipping,the solid was filtered out and dried,and then treated at high temperature.While Zn²⁺was oxidized to ZnO,the layered g-C₃N₄precursor was exfoliated into g-C₃N₄porous nanosheets loaded with ZnO nanoparticles(C₃N₄/ZnO),C₃N₄/ZnO-ZnSe was obtained after high temperature selenization treatment.The characterization results demonstrated that C₃N₄/ZnO-ZnSe exhibited higher light absorption and charge transfer efficiencies and higher CO and CH₄yields compared with pure g-C₃N₄and binary C₃N₄/ZnO or C₃N₄/ZnSe,the CH₄selectivity reached61.09%.In this study,an economical and facile synthesis strategy for C₃N₄/Zn-based composite photocatalysts was designed,which provides a rational approach for constructing efficient photocatalytic materials.(2)Design and synthesis of sulfur-doped g-C₃N₄porous nanosheets embedded with CuO-Cu_7.2S₄(S-C₃N₄/CuO-Cu_7.2S₄).The g-C₃N₄precursor was added to an ethanol solution containing Cu²⁺for dipping,the solid was filtered out and dried,and then treated at high temperature to obtain g-C₃N₄porous nanosheets loaded with CuO nanoparticles(C₃N₄/CuO),and S-C₃N₄/CuO-Cu_7.2S₄was obtained after high temperature vulcanization.This work can simultaneously realize the exfoliation of sulfur-doped g-C₃N₄porous nanosheets and the construction of ternary heterostructures.The characterization results showed that the p-n heterojunction composed of p-type semiconductor CuO,Cu_7.2S₄and n-type semiconductor sulfur-doped g-C₃N₄enhanced the separation of photogenerated carriers and prolongs their lifetime,making S-C₃N₄/CuO-Cu_7.2S₄with higher CO and CH₄yields.(3)Design and synthesis of sulfur-doped g-C₃N₄porous nanosheets embedded with SnS₂-SnO₂(S-C₃N₄/SnO₂-SnS₂).The layered supramolecular precursor was prepared by hydrothermal method and immersed in an ethanol solution containing Sn⁴⁺.The solid was dried and then treated at high temperature to obtain g-C₃N₄ porous nanosheets loaded with SnO₂nanoparticles(C₃N₄/SnO₂).After high temperature vulcanization treatment,S-C₃N₄/SnO₂-SnS₂was obtained.Such a promising synthetic strategy can simultaneously achieve the exfoliation of sulfur-doped g-C₃N₄porous nanosheets and the construction of ternary heterostructures.S-C₃N₄/SnO₂-SnS₂featured abundant active sites,enhanced CO₂adsorption capacity,improved visible light absorption efficiency,and an efficient interfacial charge transfer,the CO and CH₄yields are significantly improved,and the CH₄selectivity reached 80.30%.