Vacancy-Induced\nSymmetry Breaking in Titanium Dioxide\nBoosts the Photocatalytic Hydrogen Production from Methanol Aqueous\nSolution

The key to optimizing photocatalysts lies in the efficient\nseparation\nand oriented migration of the photogenerated carriers. Herein, we\nreport that breaking continuous TiO<sub>6</sub> tetragonal (<i>D</i><sub>4<i>h</i></sub>) symmetry in titanium dioxide\nmaterial by oxygen vacancy engineering could induce a dipole field\nwithin the bulk phase and thus facilitate the separation and transfer\nof photogenerated electron–hole pairs. After further loading\nof Cu single-atom co-catalysts, the obtained catalyst attained a hydrogen\n(H<sub>2</sub>) yield rate of 15.84 mmol g<sup>–1</sup> h<sup>–1</sup> and a remarkable apparent quantum yield of 12.67%\nat 385 nm from methanol aqueous solution. This catalyst also demonstrated\nimpressive stability for at least 24 h during the photocatalytic tests.\nThe innovative concept of producing dipole fields in semiconductors\nby breaking the crystal symmetry offers a new perspective for designing\nphotocatalysts.