Abstract: Oxygen vacancy (O V )-enriched black TiO 2 (BTO) is a promising material for supporting well-studied noble metals in the hydrogen evolution reaction (HER). Blackening TiO 2 by incorporating O V s substantially changes the electronic state of BTO and enhances HER catalytic performance compared to pristine TiO 2 . Furthermore, the incorporation of vacancies leads to deviation from a single anatase phase on a localized scale and creates a heterojunction by promoting the occurrence of localized rutile segments. Hence, synthesizing biphasic (rutile and anatase) BTO with abundant O V s and optimized Pt-metallic clusters substantially improves the electrochemical HER kinetics, though it demands a complicated multistep synthesis.

Conversely, herein, a solvent-free, single-pot green synthesis route is corroborated using a pulse laser irradiation technique to achieve the desired O v -enriched BTO structure. Controlled irradiation of anatase TiO 2 with a Pt precursor under optimized parameters in an air environment creates O V s and decorates the metal oxide with Pt nanoclusters. This defect formation decreases the activation energy of BTO, favoring the anatase phase and forming a localized rutile phase, which enhances HER activity through localized heterojunctions. The combined impacts of Pt nanoclusters and OVs revealed an outstanding specimen achieving a HER overpotential of 169 mV at 10 mA/cm 2 and a Tafel slope of 73.3 mV/dec. Importantly, long-term stability during overall water splitting was further achieved. This approach offers valuable perceptions into designing highly competent catalysts and their supporting structures for various energy-associated solicitations.