Subnanometer Size Clusters in Heterogeneous Catalysis, Electrocatalysis, and Batteries

Supported clusters made of a handful of atoms can be considered as models of the catalytic active site, and changes in the size and composition of the clusters, often just by a single (ad)atom, or changing of the support, can dramatically alter their activity and selectivity. The ligand-free clusters discussed in this chapter are synthesized in the gas phase and after mass selection deposited on oxide and carbon-based supports. The primary focus of this paper is on the performance of such size- and composition-selected subnanometer clusters in select heterogeneous catalytic and electrocatalytic reactions. The first part of the chapter aims at model heterogeneous catalysts interrogated under realistic reaction conditions of pressure and temperature using in situ X-ray characterization (scattering and absorption) combined with the monitoring of the reaction products, to correlate particle size, shape and oxidation state with catalytic performance, illustrated on the examples of propylene epoxidation, oxidative dehydrogenation of cyclohexene, CO oxidation and Fischer–Tropsch reaction. In the second section of the chapter, water splitting and cluster interactions with CO 2 under electrocatalytic conditions are discussed. The third part of the contribution deals with the performance of subnanometer clusters in Li–air batteries.