Photocatalytic reduction of CO2 Ag-BiVO4 composites modified with lignin carbon quantum dots

Abstract

Photocatalytic CO₂ reduction technology can use sunlight to convert CO₂ into fuel or chemical raw materials, slowdown the greenhouse effect and achieve sustainable development. Therefore, we have developed a series of high-quality carbon quantum dots using alkaline lignin (AL) as the core raw material and using high efficiency hydrothermal method. Ag-BiVO₄ composite was prepared by hydrothermal method. Then, the Ag-BiVO₄-CQDs photocatalytic composite was prepared by constant temperature water bath method. The structure and morphology of the composites were characterized by X-ray diffraction, transmission electron microscope and X-ray photoelectron spectroscopy. Through optical and electrochemical tests, it can be seen that the composite has better interfacial charge transfer and electron transport ability. In the visible light catalytic CO₂ reduction reaction, Ag-BiVO₄ can selectively reduce CO₂ to CH₄, and the CH₄ yield is greatly improved after Ag-BiVO₄ combines with CQDs. The 3 h CH₄ yield increased from 17.64 μmol/g to 97.82 μmol/g after reduction by adding 40 mL CQDs to Ag-BiVO₄ composite, which is 5.54 times that of Ag-BiVO₄. The results showed that the introduced CQDs were uniformly attached to Ag-BiVO₄. As an electron transport medium, CQDs can efficiently facilitate the transfer of photogenerated carriers, suppress the recombination of electron–hole pairs, and enhance the photocatalytic performance of Ag-BiVO₄-CQDs for CO₂ reduction.