Oxidation cocatalyst/S-scheme junction cooperatively assists photocatalytic H2 production in ternary hybrid: The case of PdO@TiO2-Cu2O

Abstract

Solar-driven photocatalytic hydrogen production from water splitting holds significant potential in addressing the energy crisis and environmental pollution. However, rapid recombination of photogenerated carriers and insufficient surface catalytic reaction kinetics hinder the photocatalytic process. Constructing the catalytic systems with multi-channel charge-separation can effectively alleviate those issues. In this work, ternary PdO@TiO2-Cu2O composites have been synthesized through precursor calcination and low-temperature reduction, where PdO and Cu2O nanoparticles couple with the TiO2 nanorods. Comparing to single TiO2, binary PdO@TiO2 and TiO2-Cu2O, the PdO@TiO2-Cu2O hybrid exhibits enhanced photocatalytic hydrogen production performance (5831μmol g-1h−1), with a hydrogen production rate more than three times that of single TiO2. Based on the band structures of TiO2 and Cu2O, along with the photochemical/electrochemical, in-situ EPR, Photoluminescence (PL) tests, and work function calculations, the formation of an S-scheme heterojunction at the TiO2-Cu2O interface under light illumination facilitates the recombination of electrons in the conduction band (CB) of TiO2 with holes in the valence band (VB) of Cu2O. In this regard, the established built-in electric field significantly accelerates the transfer of photogenerated charges while preserving their respective strong oxidation and reduction capabilities. Meanwhile, the introduction of PdO enriches the holes and further enhances the rate of charge separation. This S-scheme heterojunction with directional charge transfer and oxidation cocatalyst collectively form multi-channels of charge separation, optimizing charge migration and enabling efficient hydrogen production, thus improving the photocatalytic capability of pristine TiO2. This study provides a rational approach to construct efficient S-scheme heterojunction/oxidation cocatalyst multi-component catalytic systems for water splitting into hydrogen.