Construction of surface electron island by a simple organic molecule adsorption strategy: tuning the energy band structure and boosting the photocatalytic performance

Abstract

The accumulation of electrons on the surface of photocatalysts has an important impact on their energy bands and photocatalytic hydrogen evolution (PHE) process. However, how to accumulate electrons on the surface of catalysts to form electron islands remains a challenge. Herein, a super simple and green organic molecule adsorption strategy is used to construct a surface electric field on the surface of commercial TiO₂ to optimize its energy band structure and ultimately improve the photocatalytic hydrogen evolution performance. Specifically, the green, environment-friendly polyethylene glycol (PEG) is adsorbed on the TiO₂ surface by a simple mechanical grinding method. The experimental results show that the photocatalytic hydrogen evolution performance of TiO₂ can be increased by 5 times after the adsorption of polyethylene glycol. The results from the experiment and theory calculations indicated that the hydroxyl group in polyethylene glycol can provide more electrons for the TiO₂ surface. These accumulated electrons can not only cause the conduction band of TiO₂ to bend upward, thus improving its reduction ability, but also form a local electric field on the TiO₂ surface. The formed local electric field will cause the photogenerated electrons to be more concentrated, thus again improving the conduction band position and reduction ability of TiO₂. In addition, the hydroxyl group in polyethylene glycol can also improve the hydrophilicity of TiO₂ and promote the contact between TiO₂ and water molecules, which are all conducive to improving photocatalytic hydrogen evolution. This work provides a new idea and ultra-simple strategy for the improvement of photocatalytic hydrogen production performance.