C03 - Photo-/electrochemical Water Oxidation Using Metal-doped Nanoscale ZnO

Project C03 will develop zinc oxide-based nanostructures as model systems as well as the experimental methods to study and tune the photocatalytic and electrocatalytic proton-coupled water oxidation reaction at the local scale. Synthetic means to access ZnO nanoparticles doped with catalytically relevant, earth-abundant 3d transition metals will be established. Bulk characterization of the particles will be combined with initial electrochemical and photochemical studies to shed light on the surface structure, protonation states and changes thereof during the water-oxidation reaction. Mechanistic studies will focus on linking the structural features of the ZnO nanoparticles with their (photo-) electrocatalytic water oxidation performance. The effects of structural modifications on the water oxidation product selectivity, i.e. 2-proton/2-electron water-to-hydrogen peroxide oxidation vs 4-proton/4-electron water-to-oxygen oxidation, as well as their impact on the overall PCET processes will be studied by comprehensive experimental and – in collaboration – theoretical studies. Specifically, lateral- and time-resolved infrared-spectroscopic studies using scanning near-field microscopy will be used to probe the characteristic metal-oxo vibrational modes of doped ZnO, to follow structural and chemical changes of the catalyst over time. This will be achieved by developing a custom-built flow cell (a nano-reactor) where ZnO crystalline films or particles are deposited on graphene to enable operando photo- and electrochemical spectroscopic studies. In addition, the nano-reactors will allow active control of charge carrier density and electric fields. We propose that these external stimuli can be used to improve our mechanistic understanding of the PCET processes in the materials studied.