RESUMEN
Direct photoelectrochemical 2-electron water oxidation to renewable H2 O2 production on an anode increases the value of solar water splitting. BiVO4 has a theoretical thermodynamic activity trend toward highly selective water oxidation H2 O2 formation, but the challenges of competing 4-electron O2 evolution and H2 O2 decomposition reaction need to overcome. The influence of surface microenvironment has never been considered as a possible activity loss factor in the BiVO4 -based system. Herein, it is theoretically and experimentally demonstrated that the situ confined O2 , where coating BiVO4 with hydrophobic polymers, can regulate the thermodynamic activity aiming for water oxidation H2 O2 . Also, the hydrophobicity is responsible for the H2 O2 production and decomposition process kinetically. Therefore, after the addition of hydrophobic polytetrafluoroethylene on BiVO4 surface, it achieves an average Faradaic efficiency (FE) of 81.6% in a wide applied bias region (0.6-2.1 V vs RHE) with the best FE of 85%, which is 4-time higher than BiVO4 photoanode. The accumulated H2 O2 concentration can reach 150 µm at 1.23 V versus RHE under AM 1.5 illumination in 2 h. This concept of modifying the catalyst surface microenvironment via stable polymers provides a new approach to tune the multiple-electrons competitive reactions in aqueous solution.
RESUMEN
A Z-scheme photosystems combining Schottky junction and loading of applicable bandgap semiconductor is beneficial for enhancing the charge carriers' separation/transfer as well as maintain their excellent redox ability. Here, CdxZn1-xS@Au was in-situ deposited on the (010) facets of BiVO4 taking Au as a bridge for constructing a sandwich structure CdxZn1-xS@Au/BiVO4 Z-scheme photocatalyst. The electrons in BiVO4 (010) migrate unidirectionally to Au nanoparticles across the Schottky junction and effectively suppress opposite electrons flow, then be captured by the excited holes in CdxZn1-xS. Furthermore, Zn-doping also contributes to an appropriate redox ability and charge carriers separation. Benefiting from the dual-facilitated effects, the ternary CdxZn1-xS@Au/BiVO4 exhibited superior photocatalytic activity for CO2 reduction under visible light irradiation using H2O as a reducing agent, as compared with CdS and CdS@Au/BiVO4. Furthermore, the intermediate product HCOO* fixed on the surface of CdxZn1-xS@Au/BiVO4 is identified by in-situ FT-IR, playing a key role in the conversion of CO2 to CO and then improve photocatalytic selectivity.