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.

Funding/Awards:

Otto Vogl Prize for the Best Master Thesis in Chemistry from the Austrian Academy of Sciences (Jasmin Schubert)

​Collaborations involved:

Prof. Johanna Rosen and Dr. Shun Kashiwaya, Linköping University, Sweden

Publications:

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.