Rational construction of carbon-rich g-C3N4 wrapped over CePO4 nanorods: Oxygen vacancy mediated 1D/2D Z-scheme photocatalyst towards removal of congo red dye

Abstract

The rational construction of Z-scheme photocatalysts is an effective way for separating charge carriers and has gained great interest due to the potential to alleviate energy as well as environmental challenges. Here, oxygen vacancy mediated CePO4/g-C3N4 Z-scheme nanocomposite photocatalyst was developed with different mass concentration of carbon rich g-C3N4 by grinding-calcination method. The study reveals the improved crystal quality, large surface area and intimate line-to-face contact of nanocomposite essential for electronic transition between CePO4 and g-C3N4. The presence of vacancy was studied by X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) and photoluminescence (PL) spectroscopy. The total removal percentages of CR dye over CePO4/g-C3N4 (38 wt%) nanocomposite were 85% and 99% with reaction rates 3.7 and 2.8 times greater than that of pure g-C3N4 under visible and solar irradiation, respectively, and nanocomposite demonstrated good recycle stability. The superoxide radicals were found to be the main reactive species that participated dominantly in the reaction. From band structure, PL and radical trapping experiments, a Z-scheme charge transfer mechanism was proposed. The causes of improved degradation could be the result of enhanced crystal quality, improved surface area and a delay in charge carrier recombination via the Z-scheme process. This study gives a good foundation for building Z-scheme heterojunctions and sheds light to create highly active photocatalysts.