Oxygen Vacancies‐Induced Dendritic SrTiO₃/CdS p–n Heterostructures Photocatalyst for Ultrahigh Hydrogen Evolution

Abstract

Generally, hydrogen is regarded as one of the cleanest green energy sources, which can replace fossil fuels in the future due to its efficient energy release and zero-emission characteristics. [1] Photocatalytic water splitting is a promising method of hydrogen energy production. [2] As one of the most important solar technologies, semiconductor photocatalytic hydrogen production has attracted the attention of many researchers because of its environmental friendliness, stability, and economy. [3] Photosynthesis of natural plants can convert solar energy into other biological energy. The large specific surface area of the branches facilitates adequate photosynthesis, while it also requires the outside world to provide the necessary raw materials, such as dewdrops that can provide water for plants. However, there are still many challenges in the actual photocatalytic process. For example, the faster-photogenerated electron and hole complexation rates reduce the efficiency of photocatalysis, which in turn limits the practical applications of photocatalysis. [4,5] For this reason, numerous modification strategies including metal or nonmetal doping, [6,7] loading cocatalysts, [8] and construction of heterostructures [9,10] have been explored to improve photocatalytic efficiency, but there is still a huge potential for the development of lowering the carrier complexation rate in photocatalysis. Therefore, it is necessary to develop new methods to improve photocatalytic performance.SrTiO 3 is a perovskite oxide, which has a suitable band structure, high stability, superb electronic and optical performance, low toxicity, and inexpensive. [11,12] However, the broadband gap (%3.2 eV) of SrTiO 3 allows to make it merely absorb UV light, and the fast recombination of photo-generated charges carriers leads to a low usage rate of solar energy. [13] Oxygen vacancies can avoid the rapid recombination of photogenerated carriers and provide trapping sites at the same time. [14] Noticeably, oxygen vacancies can not only build a surface energy state but also expand the light absorbance to lower energy wavelengths. [15] Zhou [16] et al. found that hydrogen-treated SrTiO 3 can produce H 2 under UV light in absence of cocatalyst, due to the formation of appropriate oxygen vacancies by synergistic interaction of hydroxylation. Tan [17] et al. prepared surface oxygen vacancies on SrTiO 3 by the reaction with NaBH 4 . However, the practical application of SrTiO 3 has been greatly limited due to the low amount of hydrogen production. As a result of, it is of great meaning to explore a simple method to improve the photocatalytic hydrogen performance of SrTiO 3 .As a member of the metal sulfide family, CdS has a suitable bandgap (E g = 2.3 eV) with strong visible light absorption. [18][19][20] The inherent defects of CdS limit its practical application, such as easy photocorrosion and the high recombination rate

Tuning of TiO2/CdS Hybrid Semiconductor with Au Cocatalysts: State-of-the-Art Design for Sunlight-Driven H2 Generation from Water Splitting

“…It is imperative to investigate the activity and stability when coupling CdS with TiO 2 . Many reports suggests that stability of CdS can be enhanced by combining it with ZnO, TiO 2 , BiVO 4 , SrTiO 3 , and g–C 3 N 4 . Numerous metals, including Zn, Cu, Ag, Au, Al, Pt, Pd, Sr, and Ni have been previously utilized in combination with CdS for hydrogen generation.…”