Well-Dispersed Ruthenium in Mesoporous Crystal TiO₂ as an Advanced Electrocatalyst for Hydrogen Evolution Reaction

Abstract

TiO₂ mesoporous crystal has been prepared by one-step corroding process via an oriented attachment (OA) mechanism with SrTiO₃ as precursor. High resolution transmission electron microscopy (HRTEM) and nitrogen adsorption-desorption isotherms confirm its mesoporous crystal structure. Well-dispersed ruthenium (Ru) in the mesoporous nanocrystal TiO₂ can be attained by the same process using Ru-doped precursor SrTi_{1- x}Ru _xO₃. Ru is doped into lattice of TiO₂, which is identified by HRTEM and super energy dispersive spectrometer (super-EDS) elemental mapping. X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectroscopy (EPR) suggest the pentavalent Ru but not tetravalent, while partial Ti in TiO₂ accept an electron from Ru and become Ti³⁺, which is observed for the first time. This Ru-doped TiO₂ performs high activity for electrocatalytic hydrogen evolution reaction (HER) in alkaline solution. First-principles calculations simulate the HER process and prove TiO₂:Ru with Ru⁵⁺ and Ti³⁺ holds high HER activity with appropriate hydrogen-adsorption Gibbs free energies (Δ G_H).