Preparation of platinum-free manganese oxide (MnOx) catalyst film for H2O2 decomposition in contact-lens cleaning.

• The MnOx film prepared on the Al substrate by a hydrothermal impregnation method. • The MnOx film on the Al substrate consisted of mixed phase of MnO 2 and Mn 2 O 3. • The Pt-free MnOx/Al catalyst had high catalytic activity for H 2 O 2 decomposition. • Roughening the Al substrate improved both the catalytic activity and durability. • A conventional catalyst using Pt can be replaced with the developed MnOx catalyst. A platinum (Pt)-free manganese oxide (MnOx) catalyst film for H 2 O 2 decomposition was prepared on an aluminum (Al) substrate (MnOx/Al) by a hydrothermal impregnation method to decrease the cost of a container used in contact lens cleaning and effectively using Pt materials as other several catalysts. Scanning electron microscopy with energy dispersive X-ray spectroscopy images confirmed that the Al substrate was covered with MnOx. The thickness of the MnOx film was about 300 nm. X-ray diffraction spectra showed that the MnOx film consisted of MnO 2 and Mn 2 O 3. The catalytic activity for H 2 O 2 decomposition was estimated by measuring the residual H 2 O 2 concentration, and the target value was ≦100 ppm. The MnOx/Al catalyst was immersed in 35,000 ppm H 2 O 2 solution for 360 min, then the H 2 O 2 concentration decreased to 737 ppm. This result indicated that the MnOx catalyst had a high catalytic activity for H 2 O 2 decomposition but it was not enough for practical use. To improve the catalytic activity, an Al substrate was roughened to increase the specific surface area before preparing an MnOx film. A method with the highest effect of increase in surface roughness was a combination of sandblasting and chemical etching. An MnOx catalyst film was prepared on the roughened Al substrate (MnOx/roughened-Al). When the MnOx/roughened-Al catalyst was immersed in 35,000 ppm H 2 O 2 solution for 360 min, the H 2 O 2 concentration decreased to 38 ppm. When the catalyst was used repeatedly for 10 times, the residual H 2 O 2 concentration was 66 ppm, which indicated that the Pt-free catalyst also had high catalytic durability. These results demonstrated that a roughening was extremely effective in improving both the catalyst activity and durability of a MnOx film catalyst, and a conventional catalyst of a Pt plating film can be replaced with the developed catalyst of the MnOx film on the roughened Al substrate. [ABSTRACT FROM AUTHOR]