The performance of many contemporary photocatalysts is often limited by the fast electron-hole recombination rates and poor/unselective catalytic sites on their surface. Several strategies have been explored to address these issues, such as the use of cocatalysts – surface-attached species – that provide better-suited catalytic sites and simultaneously promote the separation of photoexcited electrons and holes. The most widely used co-catalysts are Pt, Pd, and IrO2, RuO2 for the photocatalytic reduction and oxidation of water, respectively. Given their rare nature, to achieve the large-scale industrial application of photocatalytic water splitting, the development of novel co-catalysts based on cheap and widely available elements remains an important issue.
Driven by this objective, our group has been investigating oxide-based co-catalysts based on d-block transition metals such as Mn, Co, Fe, Ni, and Cu, which are known for their excellent catalytic properties and applications in industry, research, and nature. These elements – especially in their oxide form – can undergo quick and reversible redox shuttling, accept, accumulate and release electrons – conditions necessary to generate a self-recovering system. Besides this, their surface structure and chemistry can be varied through synthetic conditions (e.g. different oxides can be generated) allowing us to further tune adsorption/desorption properties and thus their catalytic function.
Otto Vogl Prize for the Best Master Thesis in Chemistry from the Austrian Academy of Sciences (Jasmin Schubert)
Prof. Johanna Rosen and Dr. Shun Kashiwaya, Linköping University, Sweden
To this end, we applied a wet impregnation route to prepare Mn, Co, Fe, Ni, and Cu-based co-catalysts immobilized on TiO2 nanoparticles and systematically investigated their prospects in photocatalytic water splitting reactions. In contrast to the early-stage deactivation, opens an external URL in a new window discovered by our group a few years ago, we have recently provided detailed insights into the in situ Ni self-activation, opens an external URL in a new window and unraveled the active state of these co-catalysts. More recently, we took a close look into the Cu-based photosystem and unraveled thermally induced Cu diffusion, opens an external URL in a new window, which has a detrimental effect on photocatalytic performance.