A constructed 3D porous hierarchical micro-flower WO3/CdS S-scheme heterojunction for boosting photocatalytic H2O2 production and photoelectrochemical cell performance

Abstract

Constructing photocatalysts with outstanding visible light utilization efficiency and an efficient photo-generated charge transfer rate to enhance the power density and energy storage capacity in photoelectrochemical cells for hydrogen peroxide (H₂O₂) production and conversion is essential for advancing renewable energy technologies. Here, a self-powered photoelectrochemical cell is designed by using a WO₃/CdS S-scheme heterojunction as a photoanode combined with a mixture of iron phthalocyanine (Fe^IIPc) and WO₃ on carbon paper as a cathode, for effectively oxidizing H₂O to H₂O₂ and further converting H₂O₂ to supply electricity in the dark. The optimized WO₃/CdS-based cell achieves a maximum power density of 2.97 mW cm⁻² and a corresponding solar-to-electrical conversion efficiency (SECE) up to 2.12%, representing 3.8 and 8.3 times enhancement compared to the pristine WO₃-based and CdS-based ones, respectively. Furthermore, this cell can generate and store H₂O₂ (chemical energy) with the disconnected electrodes under light irradiation for 2 h, which is subsequently utilized as the fuel by the connected electrodes in the dark, yielding a specific capacitance of 29 342 mF cm⁻² and retaining 51% of the initial value after 12 h of operation. The superior WO₃/CdS-based cell activity is attributed to the improved solar utilization and effective charge separation, facilitated by the S-scheme heterostructure. Meanwhile, density functional theory (DFT) calculations and radical quenching experiment tests proved that WO₃/CdS followed the S-scheme charge transfer mechanism. Consequently, this investigation affords a useful inspiration for constructing efficient S-scheme heterojunction photocatalysts aimed at improving H₂O₂ photoelectrochemical cell performance and energy conversion efficiency.