Sensitization of TiO₂/g-C₃N₄ Heterostructures via Pd-Au Cocatalysts: A Rational Design of Water Splitting System for Green Fuel Production

The ecological impact and rising expenses of fossil fuels have led researchers to investigate alternative renewable-energy sources. Current work reported a novel and sustainable water splitting system comprising TiO₂/Pd/Au integrated on g-C₃N₄ surfaces. The phase purity and crystallization were analyzed by XRD, revealing characteristic patterns of TiO₂, g-C₃N₄, and loaded Pd-Au cocatalysts. The electronic and structural properties were analyzed by Raman spectroscopy. The efficient charge separation in Pd/Au@g-C₃N₄/TiO₂ was demonstrated by PL spectral and TRPL analyses. Interface analysis, charge transfer resistance/capacitance, and dynamics were evaluated by EIS and temporal photocurrent responses. FTIR spectra indicate the interfacial connection between g-C₃N₄/TiO₂, while UV-vis/DRS revealed that Pd/Au@g-C₃N₄/TiO₂ exhibited superior optical absorption (absorption edge at 457 nm). The BET technique confirmed the mesoporous nature of Pd/Au@g-C₃N₄/TiO₂, while SEM demonstrated its lumpy surface morphology with high dispersion of cocatalysts. The elemental compositions and electronic states were further confirmed by EDX and XPS. Hydrogen evolution activities were conducted in the sunlight using a GC equipped with TCD. Activities indicated an encouraging rate of H₂ generation on fabricated g-C₃N₄/TiO₂ heterojunctions (Z-scheme interaction) having a Au-LSPR effect along with a Pd Schottky barrier impact. The maximum H₂ evolution rate of 36.51 mmol g^-1 h^-1 (Q.E = 10.46%) was applied with 5 mg of Pd/Au@g-C₃N₄/TiO₂ in the presence of triethanolamine pH 7.5. The durability of Pd/Au@g-C₃N₄/TiO₂ catalysts was assessed by recycling tests and optimized by experimental conditions. In the current work, the hydrogen evolved by Pd/Au@g-C₃N₄/TiO₂ was ≈11.23- and 6.97-fold higher than those by bulk TiO₂ (3.25 mmol g^-1 h^-1) and g-C₃N₄ (7.87 mmol g^-1 h^-1), respectively. Based on the results, Pd/Au@g-C₃N₄/TiO₂ is recommended for reliable energy and fuel applications.