Yuhki Toku

Fabrication of Fe2O3 nanowire arrays based on oxidation-assisted stress-induced atomic-diffusion and their photovoltaic properties for solar water splitting

In this research, we propose a new simple method to fabricate high-density Fe2O3 nanowire arrays for solar water splitting, based on oxidation-assisted stress-induced atomic-diffusion. In the presence of water vapor, surface oxidation was promoted during the heating process. The driving force induced by the stress gradient was enhanced due to the expansion of the oxidation layer. Therefore, Fe2O3 nanowire arrays were fabricated at a relative low temperature (350 °C) with a high density (8.66 wire per μm2). Using the nanowire array as the photoanode, a photocurrent density of 0.65 mA cm−2 at 1.23 V vs. RHE was achieved in a three-electrode system.

Synthesis of a single-crystal Fe2O3 nanowire array based on stress-induced atomic diffusion used for solar water splitting

In this study, we successfully fabricated a single-crystal Fe2O3 nanowire array based on stress-induced atomic diffusion and used this array as the photoelectrode for solar water splitting. With the surface polishing treatment on the sample surface, the density of the Fe2O3 nanowire array reached up to 28.75 wire µm−2 when heated for 90 min at 600°C. The photocurrent density of the optimized sample was 0.9 mA cm−2 at 1.23 V versus a reversible hydrogen electrode in a three-electrode system under AM 1.5 G illumination. The incident photon-to-electron conversion efficiency was 6.8% at 400 nm.

Fabrication of multiwall carbon nanotube sheet based hydrogen sensor on a stacking multi-layer structure

In this research, we propose a new simple method to fabricate hydrogen gas sensors by stacking multiwall carbon nanotube (MWCNT) sheets. MWCNT sheets offer a larger surface area and more CNT contact, which are key factors for gas sensing, because of their super-high alignment and end-to-end structure compared to traditional CNT film. Besides, MWCNT sheets can be directly drawn from spinnable CNT arrays on large scales. Therefore, this method is a potential answer for the mass production and commercialization of CNT-based sensors with high responsivity. By stacking layers of sheets in various arrangements, the microstructure and CNT interactions in the layers were changed and their influence on gas sensing investigated. It was observed that the sample with three layers of sheet and functionalized with 3 nm thick Pd showed the best gas sensing performance, with a response of 12.31% at 4% H2 and response time below 200 s.