The photocatalytic hydrogen production performance of porous titanium dioxide, a derivative of Mil-125 (Ti), improved by using lignin-based carbon quantum

Carbon points in lignin were prepared by hydrothermal method at 180 °C for 12 h. Carbon points with diameters of 1–5 nm were observed by transmission electron microscopy. The prepared lignin carbon point solution was put into the synthesis system of Mil-125(Ti) derivative porous titanium dioxide (M–TiO₂) with 10, 15 and 20 mL, respectively, at 150 °C and 48 h to obtain CQDs/M–TiO₂ composite photocatalyst series. Through a series of characterization and analysis of its structure and morphology, it is proved that the carbon point is successfully recombined with Mil-125(Ti) derivative porous titanium dioxide (M–TiO₂). Through ultraviolet–visible-near-infrared diffuse reflection and flat band potential analysis, we determined that CQDs can improve the light absorption range of porous titanium dioxide (M–TiO₂), a derivative of Mil-125(Ti), and calculated the band structure of the material. It is proved that CQDs and Mil-125(Ti) derivative porous titanium dioxide(M–TiO₂) constitute a type I heterojunction. Photoelectrochemical analysis shows that CQDs/M–TiO₂ composite catalyst has better separation and transport efficiency than M–TiO₂ photogenerated electrons and holes. The photocatalytic hydrogen production activity test at a wavelength of > 380 nm showed that the hydrogen production rate of CQDs-15/M–TiO₂ composite reached 6715 μmol/h g, which was 5.6 times that of M–TiO₂ alone (1200 μmol/h g).