Amorphous TiO₂ doped with N was characterized by its photocatalytic activity under visible light irradiation. The amorphous N-doped TiO₂ was prepared by the sol-gel method through heat treatment at a low temperature. The photocatalyst showing activity in visible light despite heat treatment at low temperature can be applied to plastics and has excellent utility. The N-doped TiO₂ appeared amorphous when heat-treated at 130 °C. It was converted into an anatase-type N-doped TiO₂ when this was calcined at 500 °C. The photocatalyst showed photocatalytic activities in the photocatalytic decomposition of formaldehyde and methylene blue under visible light irradiation. The photocatalyst exhibited a higher rate of hydrogen production than that of TiO₂ in photocatalytic decomposition of water under liquid-phase plasma irradiation. The bandgap of the amorphous N-doped TiO₂ measured by investigation of optical properties was 2.4 eV. The lower bandgap induced the photocatalytic activities under visible light irradiation.

As bisphenol A has been found to cause hormonal disturbances, the natural biomaterial isosorbide is emerging as a substitute. In this study, a method for isosorbide synthesis from sorbitol was proposed by dehydration under high temperature and high pressure reaction. Microporous zeolites and Amberlyst 35 solid acids with various acid strengths and pore characteristics were applied as catalysts. In the synthesis of isosorbide from sorbitol, the acidity of the catalyst was the main factor. MOR and MFI zeolite catalysts with high acid strength and small pore size showed low conversion of sorbitol and low yield of isosorbide. On the other hand, the conversion of sorbitol was high in BEA zeolite with moderate acid strength. Amberlyst 35 solid acid catalysts showed a relatively high conversion of sorbitol, but low yield of isosorbide. The Amberlyst 35 solid acid catalyst without micropores did not show any inhibitory effects on the production of by-products. However, in the BEA zeolite catalyst, which has a relatively large pore structure compared with the MOR and MFI zeolites, the formation of by-products was suppressed in the pores, thereby improving the yield of isosorbide.

This study examined the H₂ production characteristics from a decomposition reaction using liquid-phase plasma with a bismuth ferrite catalyst. The catalyst was prepared using a sol–gel reaction method. The physicochemical and optical properties of bismuth ferrite were analyzed. H₂ production was carried out from a distilled water and aqueous methanol solution by direct irradiation via liquid-phase plasma. The catalyst absorbed visible-light over 610 nm. The measured bandgap of the bismuth ferrite was approximately 2.0 eV. The liquid-phase plasma emitted UV and visible-light simultaneously according to optical emission spectrometry. Bismuth ferrite induced a higher H₂ production rate than the TiO₂ photocatalyst because it responds to both UV and visible light generated from the liquid-phase plasma.