Photocatalytic and photoelectrocatalytic hydrogen generation from water splitting by utilizing the visible spectrum of sunlight has been recognized as one of the promising energy conversion applications. Herein, we report the three-dimensional (3D) superstructure of g-C 3 N 4 and reduced graphene oxide embedded with Rh-doped SrTiO 3 nanoparticles as ternary aerogels for efficient hydrogen production. The optimized aerogel exhibits high competency for visible light harvesting due to the unique 3D morphology and shows excellent hydrogen evolution performance with quantum efficiencies of 51.1 and 26.9% at 450 and 600 nm monochromatic wavelengths, respectively. The 3D arrangement of integrated components helps in enhanced light absorption due to multiple reflections of incident light within the system and provides a high surface area with abundant reaction sites. Moreover, the ternary heterojunction facilitates efficient charge transfer owing to the suitable band positions of each component as evidenced by fluorescence lifetime, photocurrent, and impedance spectroscopic measurements, resulting in enhanced photocatalytic performance. In addition, the photoelectrocatalytic hydrogen evolution activity reveals the multifunctional nature of the synthesized catalysts. Thus, the hybrid design of the photocatalytic system realizes efficient hydrogen production in suspension and demonstrates the potential of aerogel-based materials as next-generation photocatalysts.
Defects in crystal structures often contribute to an increase in the number of catalytically active sites and, in turn, enhance the electrochemical performances. In the present work, we modulate the phase transition of tungsten oxide from hexagonal to the monoclinic by tuning annealing conditions in vacuum environment. This phase transition also accompanies the incorporation of oxygen vacancies in crystal structures. WO3‐x annealed at 550 °C (Vac‐550) shows a transition from heaxagonal to monoclinic with superior hydrogen evolution activity, exhibiting a Tafel slope of only 30 mV/dec, which is comparable that of commercial Pt/C. XRD, in situ TEM, EPR, and XPS analysis provide detailed insights into the structural transition as well as oxygen vacancy concentration of the annealed WO3‐x samples in a vacuum environment. This work paves the way towards a generalized methodology for enhancing electrochemical activity by the vacancy modulation in transition‐metal oxides.
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