Cu<sub>2</sub>Oナノ構造体の形状最適化および表面修飾による太陽光水分解変換効率の向上

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  • Enhancement of Solar-to-hydrogen Conversion Efficiency in Water Splitting by Optimizing Morphology of Cu<sub>2</sub>O Nanostructure and Surface Modification

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<p>Recently, Cu2O has been considered as an attractive material for solar water splitting due to its excellent characteristics such as small bandgap, visible light adsorption, abundance, and nontoxicity. The theoretical solar-to-hydrogen conversion efficiency (STH) of Cu2O is 18% for water splitting. To date, the value experimentally obtained by previous works has not attained and overcomed above ideal value, because of the lack of Cu2O in photocathode to absorb sunlight efficiently, the short diffusion length of minority cariers, and the Cu2O photocorrosion during water splitting. 3D nanostructures for water splitting and surface modification contribute to resolving these issues. Nanostructures can improve STH owing to high surface-to-volume ratio and short diffusion length for carrier transport compared with bulk materials. In addition, surface modification enables to promote the separation of photogenerated electron-hole pair and to protect the photoelectrode against photocorrosion, and thus resulting in the enhancement of stability in Cu2O photocathode. The present study aimed to improve STH and stability in Cu2O photocathode for water splitting by optimizing morphology of Cu2O nanostructures and surface modification. In order to determine the suitable conditions for water splitting, the relationship between the morphology of the structure and STH was examined. The photocathode with Cu2O nanostructures exhibited maximum photocurrent density of 4.58 mA/cm2 at a potential of 0 V vs. reversible hydrogen electrode (RHE) and STH of 5.63%. Besides, surface modification was successfully introduced by covering nanostructures with homogeneous and conformal layers formed by atomic layer deposition (ALD).</p>

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