Escalating the Catalytic Water Splitting on Si–gC₃N₄/Al–rTiO₂ System: Synergy between SPR and Charge Transfer

Hybrid photocatalytic systems have drawn significant attention to produce renewable hydrogen from water splitting. High performances of hybrid catalysts depend upon synergism and effective charge transfer, specifically during the photoreaction. In this work, Cu–Fe-loaded dual-doped hybrid Si–gC3N4/Al–rTiO2 catalysts have been synthesized and introduced. Cu–Fe cocatalysts were deposited by coprecipitation and chemical reduction, whereas Si and Al doping was in situ achieved on hydrothermal reactions. Catalysts were abbreviated as Cu–Fe@Si–CN/Al–TO, where CN = gC3N4 and TO = rTiO2. Morphology and optical characteristics have been evaluated by X-ray diffraction (XRD), Raman, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–vis/drs, photoluminescence (PL), electron dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS), whereas the electrochemical response has been justified via electron impedance spectroscopy (EIS) technique. All photoreactions have been performed in a quartz reactor (150 mL/Velp-UK), whereas hydrogen evolution activities have been monitored on a gas chromatograph (GC–TCD/Shimadzu-Japan). Results depict that existence of Al dopants reduced the band gap of rTiO2 and has extended its photon/light absorption capability. The Si dopants in gC3N4 sheets enhance the overall electron transfer by contributing relatively higher charge induction to active sites. It has been predicted that Cu generates high-energy electrons (i.e., surface plasmon resonance, SPR-induced charges) that progressively transfer to Si–gC3N4, where they are dragged to Al–rTiO2 via Fe cocatalysts that act as an electron mediator. Although there are many challenges ahead, the aforementioned catalyst has potential to replace the costly and conventional catalysts that have been priorly used for hydrogen generation technologies.