Constructing BiOBr/CoOx/g-C3N4 Z-scheme photocatalyst with CoOx as both redox mediator and cocatalyst for phenol degradation

Abstract

Constructing Z-scheme heterostructure photocatalysts is an efficient method to improve the photocatalytic performance for degrading organic pollutants. Herein, the BiOBr/CoOx/g-C3N4 Z-scheme photocatalyst was constructed by integrating two-dimensional (2D) BiOBr and g-C3N4 components with introducing CoOx as both redox mediator and cocatalyst. The spectroscopic and photoelectrochemical analyses verified the higher efficiency of charge transfer and separation in the BiOBr/CoOx/g-C3N4 heterostructures. For photocatalytic degradation of phenol in water, the BiOBr/CoOx/g-C3N4 photocatalyst exhibited an apparent rate constant of 0.0579 min−1, which is 7.3, 4.3 and 3.0 times those from g-C3N4, BiOBr, and BiOBr/g-C3N4 samples, respectively. As identified by the control experiments and the in-situ electron spin resonance measurements, the photogenerated holes (h+), hydroxyl radical (·OH) and superoxide radical (·O2−) contributed together to the photocatalytic phenol degradation. The enhanced photocatalysis of BiOBr/CoOx/g-C3N4 heterostructures was attributed to its multiple virtues of broad photoabsorption region as well as favorable spatial separation and sufficient redox potentials of electrons and holes. The CoOx species could serve as a charge mediator to accelerate the interfacial charge transfer and a cocatalyst to promote the hole-driven oxidation reaction. This study develops a low-cost and high-efficiency photocatalyst for the removal of organic pollutants from aquatic environment as well as highlights an effective approach for the construction of all-solid-state Z-scheme photocatalyst.