In-situ Photoluminescence, Raman, and IR Spectral Study of Porous Silicon during Exposure to Thermoelectrons/H atoms

Photoluminescence (PL), Raman, and transmission IR spectral measurements of porous silicon (PS) have been carried out during exposure to thermoelectrons and also subsequent exposure to H atoms, H 2 O and O 3 . The PL band of as-anodized PS was significantly decreased by the first exposure to thermoelectrons accompanied by the intensity reduction of the IR bands due to hydrogenated Si species (Si-H x ; x ¼ 1{3). Upon subsequent exposure to H atoms the PL band intensity was almost recovered but never exceeded its original intensity. This PL recovery was accompanied by re-generation of Si-H x bonds. In contrast, an overshooting recovery in the PL intensity took place when thermoelectron-treated PS was exposed to H 2 O or O 3 . The obtained IR spectra showed that Si-O and/or Si-OH bonds were formed at the PS surface. These results demonstrate that the PL of the PS is quite sensitive to the oxygen-included surface bonds

Surface microstructures and oxygen evolution properties of cobalt oxide deposited on Ir(111) and Pt(111) single crystal substrates

Abstract We investigated the oxygen evolution reaction (OER) activity changes of cobalt oxide (CoOx) thin films on Ir(111) and Pt(111) substrates by repeated OER measurements in 0.1 M KOH. Atomic force microscopy and X‐ray photoelectron spectroscopy analysis of the as‐prepared CoOx/Ir(111) and CoOx/Pt(111) showed similar surface morphologies of the CoOx thin films and almost the same OER overpotentials, which were estimated to be around 430 mV. However, after three OER measurements, the overpotential of CoOx/Ir(111) decreased by 70 mV, whereas that of CoOx/Pt(111) increased slightly. Structural analysis showed that CoOx/Ir(111) revealed the island‐like nanostructures of CoOx dispersed on Ir(111) surface, accompanied by the generation of CoOOH. In contrast, for CoOx/Pt(111), the Pt(111) substrate remains covered by the CoOx thin film. The results suggest that the interaface at CoOx (CoOOH) nano‐islands and Ir(111) substrate are responsible for reducing the OER overpotential