Probing Hydrogen\nEvolution on Pulsed Laser-Crafted\nPt-Infused Oxygen-Deficient Black TiO<sub>2</sub> in Real-Time Using\nRaman Spectroscopy

Oxygen vacancy (O<sub>V</sub>)-enriched black TiO<sub>2</sub> (BTO)\nis a promising material for supporting well-studied noble metals in\nthe hydrogen evolution reaction (HER). Blackening TiO<sub>2</sub> by\nincorporating O<sub>V</sub>s substantially changes the electronic\nstate of BTO and enhances HER catalytic performance compared to pristine\nTiO<sub>2</sub>. Furthermore, the incorporation of vacancies leads\nto deviation from a single anatase phase on a localized scale and\ncreates a heterojunction by promoting the occurrence of localized\nrutile segments. Hence, synthesizing biphasic (rutile and anatase)\nBTO with abundant O<sub>V</sub>s and optimized Pt-metallic clusters\nsubstantially improves the electrochemical HER kinetics, though it\ndemands a complicated multistep synthesis. Conversely, herein, a solvent-free,\nsingle-pot green synthesis route is corroborated using a pulse laser\nirradiation technique to achieve the desired O<sub>v</sub>-enriched\nBTO structure. Controlled irradiation of anatase TiO<sub>2</sub> with\na Pt precursor under optimized parameters in an air environment creates\nO<sub>V</sub>s and decorates the metal oxide with Pt nanoclusters.\nThis defect formation decreases the activation energy of BTO, favoring\nthe anatase phase and forming a localized rutile phase, which enhances\nHER activity through localized heterojunctions. The combined impacts\nof Pt nanoclusters and O<sub>V</sub>s revealed an outstanding specimen\nachieving a HER overpotential of 169 mV at 10 mA/cm<sup>2</sup> and\na Tafel slope of 73.3 mV/dec Importantly, long-term stability during\noverall water splitting was further achieved. This approach offers\nvaluable perceptions into designing highly competent catalysts and\ntheir supporting structures for various energy-associated solicitations.