Cold Gas Sprayed TiO2-Based Electrodes for the Photo-Induced Water Oxidation
AbstractCold gas spraying (CGS) is presented as an innovative approach to deposit semiconductor particles onto substrates in order to form photoelectrodes for electrochemical applications. Thin layers of TiO2 (P25-20 by Evonik Industries) are deposited onto titanium substrates (TiO2-CGS films) at different temperatures of the gas carrier within the CGS process (300 - 1000 °C). Structural characterization reveals unchanged bulk properties of the TiO2 nanoparticles. Clearly, the short duration time of the CGS process hinders crystalline bulk changes of the TiO2 particles in the hot gas stream. However, surface photovoltage measurements indicate that the CGS process modified defect states at the surface when exposed to different gas temperature. In photoelectrochemical measurements TiO2-CGS films yield seven times higher photocurrents and IPCE values than comparable films prepared by the well-established doctor blade technique. The increased efficiency might be due to an enhanced particle to substrate bonding caused by particles welding to the metallic substrate during the cold gas spray process.