In catalysis it is mandatory to have as many active sites as possible at the surface in order to maximize the active surface area. This is obtained by forming nanoparticulate catalysts, in particular clusters and small nanoparticles. We aim to make new and efficient catalysts for HER, OER, and the hydrogenation of CO2 by accessing the non-scalable size regime, i.e. the cluster regime and the transition regime (cluster-nanoparticle transition regime). Since the activity may change radically with particle size in these two size regimes, it is essential to fully control the exact size and composition. This can be achieved by using state-of-the-art clusters sources (laser ablation or sputter magnetron cluster source combined with mass-selection) offering entirely new structures and compositions of metals, alloys, oxides or even sulfides, which are simply not accessible by conventional synthesis methods. Interestingly, the synthesis method proposed here can open up entirely new reaction pathways, if we were to modify a “cluster or transition entity” by adding another atom with a different composition i.e. another element. An additional advantage of such “clusters and transition entities” is the existence of unsaturated bonds that can facilitate the bonding to the substrate. This could prove to be an interesting route to reduce the serious problem of diffusion and subsequent coalescence. In summary, the concept is to synthesize mass-selected “clusters and transition entities”, deposit them on well-defined semiconductor surfaces (TiO2, Ta3N5, MoS2, WSe2), upon which we can characterize them using the most advanced methods available at TUM and DTU and also measure their photocatalytic reactivity towards the reactions defined above. Exploring the activity of such “clusters and transition entities” particularly at ambient conditions, in the liquid phase or under the influence of electromagnetic irradiation and/or electric fields is largely unexplored, and clearly beyond the current state-of-the-art.
In this workshop progress that has been made in the groups working at DTU and TUM will be presented.