The Mars–Van Krevelen cycle and non-noble metal Ni jointly promoting Z-scheme charge transfer: a study on the photothermal synergy effect applied in selectively oxidizing aromatic alcohols

Abstract

Photothermal catalysis is a promising method for selectively oxidizing organic compounds, effectively addressing the energy-intensive and low-selective processes of thermal catalysis, as well as the slow reaction rates of photocatalysis. In this study, a ternary photothermal catalyst, Ni/CeO₂/CdS, was synthesized using a simple calcination and solvothermal method. The catalyst demonstrated remarkable improvement in reaction rates and achieved nearly 100% selectivity in converting benzyl alcohol to benzaldehyde through photothermal catalysis at normal pressure. The reaction rates were 5.9 times and 63 times higher than those of CdS and Ni/CeO₂ individually. XPS analysis confirmed that the thermal catalysis followed the Mars–Van Krevelen (MVK) mechanism and also proved that photocatalysis facilitated the MVK cycle. Additionally, DFT calculations showed that Ni acted as an electron transfer channel, facilitating efficient Z-scheme charge transfer. The in situ infrared technique was used to dynamically monitor the reaction process and explain the high selectivity of the product. Furthermore, detailed explanations of photocatalysis, thermocatalysis, and photothermal synergistic catalysis were proposed based on the aforementioned characterization and theoretical calculations. This approach establishes a theoretical foundation for the development of efficient photothermal catalysts.