Abstract:
Hydrogen peroxide (H2O2) is a powerful oxidant that directly or
indirectly oxidizes many organic and inorganic contaminants. The photocatalytic generation of H2O2 is achieved by using a semiconductor photocatalyst
in the presence of alcohol as a proton source. Herein, we have synthesized
oxygen vacancy (Ov)-mediated TiO2/B-doped g-C3N4/rGO (TBCN@rGO)
ternary heterostructures by a simple hydrothermal technique. Several characterization techniques were employed to explore the existence of oxygen vacancies
in the crystal structure and investigate their impact on the optoelectronic
properties of the catalyst. Oxygen vacancies offered additional sites for
adsorbing molecular oxygen, activating alcohols, and facilitating electron
migration from TBCN@rGO to the surface-adsorbed O2. The defect creation
(oxygen vacancy) and Z-scheme mechanistic pathways create a suitable
platform for generating H2O2 by two-electron reduction processes. The
optimized catalyst showed the highest photocatalytic H2O2 evolution rate of
172 μmol/h, which is 1.9 and 2.5 times greater than that of TBCN and BCN, respectively. The photocatalytic oxidation of various
lignocellulose-derived alcohols (such as furfural alcohol and vanillyl alcohol) and benzyl alcohol was also achieved. Photocatalytic
activity data, physicochemical and optoelectronic features, and trapping experiments were conducted to elucidate the structure−
activity relationships. The TBCN@rGO acts as a multifunctional Z-scheme photocatalyst having an oxygen vacancy, modulates
surface acidity−basicity required for the adsorption and activation of the reactant molecules, and displays excellent photocatalytic
performance due to the formation of a large number of active surface sites, increased electrical conductivity, improved charge transfer
properties, outstanding photostability, and reusability. The present study establishes a unique strategy for improving H2O2
generation and alcohol oxidation activity and also provides insights into the significance of a surface vacancy in the semiconductor
photocatalyst.
