Ultrasonic-Induced Surface Disordering Promotes Photocatalytic Hydrogen Evolution of TiO2

Surface disordering has been considered an effective strategy for tailoring the charge separation and surface chemistry of semiconductor photocatalysts. A simple but reliable method to create surface disordering is, therefore, urgently needed for the development of high-performance semiconductor photocatalysts and their practical applications. Herein, we report that the ultrasonic processing, which is commonly employed in the dispersion of photocatalysts, can induce the surface disordering of TiO₂ and significantly promote its performance for photocatalytic hydrogen evolution. A 40 min ultrasonic treatment of TiO₂ (Degussa P25) enhances the photocatalytic hydrogen production by 42.7 times, achieving a hydrogen evolution rate of 1425.4 μmol g^-1 h^-1 without any cocatalyst. Comprehensive structural, spectral, and electrochemical analyses reveal that the ultrasonic treatment induces the surface disordering of TiO₂, and consequently reduces the density of deep electron traps, extends the separation of photogenerated charges, and facilitates the hydrogen evolution reaction relative to oxygen reduction. The ultrasonic treatment manifests a more pronounced effect on disordering the surface of anatase than rutile, agreeing well with the enhanced photocatalysis of anatase rather than rutile. This study demonstrates that ultrasonic-induced surface disordering could be an effective strategy for the activation of photocatalysts and might hold significant implications for the applications in photocatalytic hydrogen evolution, small molecule activation, and biomass conversion.