Oxygen vacancies-rich black titania derived from TiO₂(B) enhances hydrogen spillover for hydrogen evolution reaction electrocatalysis

Using traditional TiO₂ as a support for platinum-based electrocatalysts in the hydrogen evolution reaction (HER) has been limited by its inherently low electrical conductivity and lack of defect sites. In this study, a defective black TiO₂ (b-TiO₂) support is synthesized from bronze-phase TiO₂(B) with a 2D nanostructure. The resulting b-TiO₂ undergoes a phase transition to anatase, showing improved electrical conductivity (2.54 × 10⁻⁵ S cm⁻¹), a low band gap of 2.5 eV, and a high concentration of oxygen vacancies. This b-TiO₂ serves as a support for PtNi alloy HER catalysts with low Pt loading (5 wt%) in both acidic and alkaline environments. The investigation of the Pt:Ni mass ratio indicates that an optimal ratio of 5:2 yields the highest HER activity. Furthermore, the presence of oxygen vacancies in b-TiO₂ enhances the strong metal–support interaction (SMSI) and acts as hydrogen-capture sites, thereby facilitating hydrogen spillover from PtNi to the support during HER, as confirmed by in situ Raman spectroscopy. Consequently, the optimized PtNi/b-TiO₂ catalyst demonstrates outstanding HER activity, with low overpotentials of 16 mV in 0.1 M HClO₄ and 19 mV in 1.0 M KOH, surpassing commercial Pt/C. The PtNi/b-TiO₂ catalyst also exhibits excellent durability, maintaining stable chronopotentiometry for more than 100 h in both electrolytes. This work successfully introduces defective b-TiO₂ support with great potential for developing high-performance electrocatalysts.