Tuning Oxygen Vacancy Density in TiO2 Hosts for Stabilizing Nanoscale Pt Species and Enhancing Hydrogen Evolution

Abstract

Developing efficient electrocatalysts for the hydrogen evolution reaction (HER) with improved noble‐metal utilization is essential for sustainable hydrogen production. Here, defect‐engineered TiO2−x supports were developed to stabilize dispersed Pt nanoparticles (∼5 nm) and regulate metal–support interactions. Oxygen vacancies were introduced through controlled NaBH4 reduction, enabling systematic modulation of Ti3+ and vacancy concentrations while preserving the anatase structure. Structural and spectroscopic analyses reveal that TiO2−x(0.2) possesses an optimal defect density, providing electron‐rich anchoring sites for Pt and strengthening interfacial electronic coupling. Consequently, Pt/TiO2−x(0.2) exhibits enhanced HER activity in acidic media, requiring an overpotential of ∼65 mV at 10 mA cm−2 with a Tafel slope of ∼85 mV dec−1. Electrochemical impedance and CO chemisorption measurements further indicate improved charge‐transfer kinetics and increased accessibility of Pt active sites. In contrast, excessive defect formation in Pt/TiO2−x(0.4) induces structural disorder and an unfavorable electronic environment, resulting in reduced activity despite its higher surface area. These findings demonstrate that optimizing defect density, rather than simply maximizing defects, is critical for controlling metal–support interactions and maximizing Pt utilization in oxide‐supported HER electrocatalysts.