Krystian Mróz has received his PhD degree. Congratulations!
The impact of modifications on the electronic structure of semiconductor photocatalysts in the context of light to chemical energy conversion
The doctoral thesis focuses on the structural modifications of semiconductors such as zinc sulfide and titanium dioxide to improve their photocatalytic efficiency in water and carbon dioxide reduction processes. Specifically, the aim of the study was to investigate the effect of modifications on the distribution of the density of electronic states within the bandgap and the photophysical mechanisms that determine the photocatalytic activity of these materials. In the course of the work, an optimal method for synthesizing ZnS with an excess of thiourea was developed, leading to the production of a material with the highest photocatalytic activity. Additionally, it was shown that surface modifications of ZnS using noble metals can affect its electronic structure, but they lead to an acceleration of charge recombination, limiting the photocatalytic activity, except for the platinum modifier, which has a positive effect. In the next stage, doping ZnS with Cu²⁺ ions was studied, which significantly increased the material’s activity both in the ultraviolet and visible light ranges. The phenomenon of activation of Cu-ZnS materials under UV light exposure was also investigated in terms of the nature of the electronic states introduced by copper atoms. The final part of the work focused on the study of thin-film heterojunctions of CuxO-TiO2 to increase the activity of TiO2 in CO2 reduction. The results showed that TiO2@CuO and Cu2O@TiO2 heterojunctions exhibit interesting photocatalytic properties. Furthermore, the direction of the flow of photogenerated charges within the photocatalyst was examined, confirming the formation of an “S-scheme” heterojunction. This work provides new insights into the impact of various structural and chemical modifications on the photocatalytic properties of ZnS and TiO2, emphasizing the importance of controlling electronic states and photophysical mechanisms to improve the efficiency of CO2 and H2O reduction processes. The proposed approach represents an important step toward the development of more efficient photocatalysts.