Catalysts are a critical component for chemical reactions in industrial applications. They are able to optimize selectivity, efficiency and reactions rates thus enabling more environmentally friendly processes.
This work presents a novel approach to catalyst functionalisation for the CO{2} reduction reaction by combining the reactive species of an atmospheric pressure plasma jet with the electric fields and energy input of a laser. This leads to both, a nanoscale structuring as well as a controllable chemical composition of the surface, which important parameters for optimizing catalyst performance. The treatment is conducted on thin copper layers deposited by high power pulsed magnetron sputtering on silicon wafers.
Because atomic oxygen plays a key role in oxidizing copper, two photon absorption fluorescence is used to investigate the atomic oxygen density in the interaction zone of the COST plasma jet and a copper surface. The used atmospheric pressure plasma jet provides an atomic oxygen density at the surface in a distance of 8 mm to the jet nozzle of approximately 2x10211/m3 or a flux of 2x1023 1/m2s$.
Pulsed laser induced dewetting is used to form nanoparticles from the deposited copper layer, to enhance catalytic performance. Varying the layer thickness allows to control the size of the particles. A gas flow directed on the sample during the combined treatment disturbes the particle formation. This can be prevented by increasing the laser energy to compensate the cooling effect of the gas flow.
Investigating the surface using x-ray photoemission spectroscopy reveals, that the untreated copper layer surface consists mostly of metalic copper and Cu(I) oxide. Irradiating the sample only with the laser did not change the composition. The combination of plasma and laser treatment is able to produce the Cu(II) species like CuO, whose concentration increases with treatment time. The presented process allows the tuning of the ratio of C2O / CuO, which is an interesting parameter for further studies on copper catalyst performance.