Direct Z-scheme based WS2/TiO2 heterostructures for hydrogen evolution reactions

Abstract

Hydrogen as a clean fuel is increasingly sought after for its potential to replace non-renewable energy sources, with the hydrogen evolution reaction (HER) presenting a sustainable method for its production. This study focuses on enhancing HER efficiency through the fabrication of a Z-scheme based tungsten di sulfide/titanium di oxide (WS2/TiO2) heterostructure via hydrothermal synthesis. Transition metal dichalcogenides like WS2, known for their unique properties, are integrated with TiO2 nanorods to create a robust photocatalytic system. Characterization techniques such as X-ray diffraction (XRD), Raman spectroscopy, Field-emission scanning electron microscopy (FE-SEM) and Brunauer-Emmett-Teller (BET) were performed. X-ray photoelectron spectroscopy (XPS) and Ultraviolet photoelectron spectroscopy (UPS) provided comprehensive insights into the electronic interactions and charge transfer kinetics. A shift in peak positions in XPS spectra indicate the enhancement in catalytic active sites which is in corroboration with the UPS studies. An altered energy environment causing the Z-scheme charge transfer in heterostructure was proved, enhancing the hydrogen production. From the UPS studies, a lower work function for heterostructure i.e. 5.47 eV as compared to 5.5 eV for pristine WS2 indicates improvement in charge transfer. Electrochemical measurements including linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) confirmed the improved HER performance of heterostructure with lower value of onset potential (0.031 V) and charge transfer resistance (3.5 k Ω) as compared to pristine samples. Thus, proving WS2/TiO2 heterostructure to be a potential candidate for sustainable hydrogen production. © 2024 Hydrogen Energy Publications LLC