Surface-engineering of decahedron shaped bismuth vanadate for improved photoelectrochemical water oxidation by indium doping coupled with graphitic carbon nitride quantum dots

Abstract

Surface of a photocatalyst critically determines the efficiency of water oxidation by providing suitable reaction sites and energetics. Manipulating the properties of semiconductor surface for better charge extraction and efficiency forms the basis of present study. We chose monoclinic BiVO4 as a model system, due to its suitable band structure and stability with a theoretical current density approaching 7 mA/cm2 is a promising material for photoelectrochemical water oxidation. An in-situ growth procedure yields, indium doped BiVO4 (BiVO4:In) photoanode with distinctive morphology. This photoanode forms a type II heterojunction (BiVO4:In)-CNQD) with g-C3N4 quantum dots (CNQD) loading to address the shortcomings. A photocurrent density of ~2.42 mA/cm2 with a solar to hydrogen conversion of 2.66% with an average Faradaic yield of 90% is yielded, which is ~4-folds higher than its bare counterpart. (BiVO4:In)-CNQD photoanode shows a significant cathodic shift of 136 mv than bare BiVO4 photoanode. Indium in BiVO4 favors the creation of oxygen vacancies, which improves charge separation and charge carrier density in BiVO4:In photoanode. It is also observed that the BiVO4:In photoanode shows higher surface hydrophilic characteristics, results in more polar surface and water adsorption on the surface, leading to more active water at the reaction site.