Unraveling the structural phase transition and electrochemical water splitting of LaVO₄/Pd-gC₃N₄ nanocomposite

The development of cost-effective and efficient bifunctional electrocatalysts is vital for sustainable hydrogen production via electrochemical water splitting. In this study, we report the synthesis of a nanorod-shaped lanthanum vanadate (LaVO₄, LaV) integrated with palladium-doped graphitic carbon nitride (Pd-gCN) to form a hybrid LaV/Pd-gCN composite catalyst. Synchrotron X-ray diffraction (SXRD) reveals that LaV crystallizes in a monazite-type structure and undergoes a subtle structural transformation when combined with Pd-gCN, enhancing its catalytic properties. The incorporation of Pd with graphitic carbon nitride (g-C₃N₄) significantly improves its electrical conductivity and introduces additional active sites, facilitating charge transfer and reaction kinetics. Electrochemical analysis demonstrates outstanding bifunctional performance of the LaV/Pd-gCN composite, with low overpotentials of 290 mV for the hydrogen evolution reaction (HER) and 410 mV for the oxygen evolution reaction (OER) at 100 mA cm^-2 in alkaline media. The composite also exhibits excellent stability, retaining over 85 % of its initial activity after 100 h of continuous operation for both HER and OER. The enhanced performance is attributed to the synergistic interaction among La, V, Pd, and the g-C₃N₄ matrix, which promotes favorable electronic structures and interfacial charge transfer. These findings highlight the potential of LaV/Pd-gCN as a promising bifunctional electrocatalyst for overall water splitting, offering a viable alternative to noble metal-based systems.