Facile synthesis of surface oxygen vacancy and Ti³⁺ defects in SrTiO₃ perovskite coupled g-C₃N₄ decorated with Au ternary nanocomposites for enhancing electrocatalytic activity from acidic and natural seawater conditions

The development of efficient electrocatalysts became vital to resolving the ongoing clean energy crises and environmental issues, wherein high-performance catalysts for the improved electrocatalytic hydrogen evolution reaction (EHER) are demanded. To meet this goal, an advanced and green ultrasonic-assisted pulsed laser ablation in liquid technique was used to prepare surface oxygen vacancy and Ti³⁺ defects in perovskite-based ternary nanocomposites (PTNCs) decorated with Au@SrTiO₃/g-C₃N₄. An effective cathode was designed using Au@SrTiO₃/g–C₃N₄–decorated PTNCs for EHER that operated in an acidic media of 0.5 M H₂SO₄. The optimized Au@SrTiO₃/g-C₃N₄ PTNCs revealed an improved EHER at a very low over-potential of 0.082 V at a cathodic current density (J) of −10 mA/cm², high double-layer capacitance (679.8 μF/cm²), large electrochemical surface area (19.4 cm²), high mass activity (198.35 A/g), high specific activity (2.91 mA/cm²), high surface charge density (0.0404 C/cm²), high catalytic active sites (4.19 × 10⁻⁷ mol/cm²), and exceptional long-term stability at 50 h, respectively. The Tafel slope of 45.36 mV/dec confirmed the presence of the Volmer-Heyrovsky mechanism to explain the enhanced EHER cycle of the prepared PTNCs. The improved electrocatalytic EHER performance was attributed to the induced synergistic strong metal-support interaction (SMSI) effect of the surface oxygen vacancy and Ti³⁺ defects in PTNCs that increased electrochemical surface area, high exposure of abundant active sites, improved intrinsic kinetics, and fast charge transport, respectively. Moreover, Au@SrTiO₃/g–C₃N₄–decorated PTNCs exhibit excellent natural seawater electrolysis in terms of EHER at a low over-potential of 0.300 V at a J = −10 mA/cm² and long-term stability at 10 h, respectively. It is demonstrated that the proposed novel surface oxygen vacancy and Ti³⁺ defects in Au@SrTiO₃/g-C₃N₄ PTNCs are effective electrocatalysts can be beneficial for producing hydrogen from green technologies in future energy applications via interface engineering.