Simultaneously Utilizing Excited Holes and Electrons for Piezoelectric-Enhanced Photoproduction of H2O2 from S-Scheme 2D S-doped VOx/g-C3N4 Nanostructures

Abstract

The simultaneous use of excited holes and electrons in photocatalytic research has become a strong driving force for rationalizing materials in design and development. As a promising strategy, step-scheme (S-scheme) photocatalysts have enormously ignited the photocatalytic community in recent decades. Introducing piezoelectric fields under light irradiations to generate valuable chemical products, such as hydrogen peroxide (H2O2), has also gained current interest in enhancing the large-scale production of these chemicals. In the research, we reported the fabrication of 2D S-doped VOx deposited on 2D g-C3N4 to produce H2O2 via the piezo-photocatalytic process. The finding pointed out that adding sulfur to VOx can help improve the catalytic outcomes by modifying the electronic and morphological properties of pristine VOx. In addition, when coupled with g-C3N4, the presence of sulfur limits the formation of graphene in the VOx/g-C3N4 composites, causing shielding effects in the materials. Besides, the research also sheds light on the charge transportation between g-C3N4 and S-VOx under irradiation and how the composites work to trigger the formation of H2O2. It turned out that the formation of H2O2 significantly relies on the reduction of oxygen to generate oxygenic radical species at g-C3N4 sites. Meanwhile, S-VOx provides oxidative sites in the composites to oxidize water molecules to generate H2O2. This study confirms the validation of S-scheme piezo-photocatalysts, thus encouraging further research on developing heterojunction materials with high catalytic efficiency, which can be used in practical conditions.