Study of photocatalytic decomposition of hydrogen peroxide over ramsdellite-MnO2 by O2-pressure monitoring

The catalytic and photocatalytic activities of ramsdellite type manganese oxide, R-MnO2 were studied from the initial rate of decomposition of H2O2 in aqueous solution. The kinetic study was followed by the production of O2via gas pressure monitoring (O2-monitored method), in the dark and under visible light irradiation (λ ≥ 400 nm), at 20 °C. Experimental data showed that the rate of H2O2 decomposition, under visible light irradiation and in the dark, obeys the first order kinetic law. While in the dark the H2O2 decomposition rate by mass unit was around 6.88 mmol g−1 s−1, under visible light irradiation the H2O2 decomposition rate achieved a maximal value of 15.13 mmol g−1 s−1. The increase in the H2O2 decomposition, by effect of the visible light, was observed in ranges of catalyst concentrations from 16 to 374 mg L−1. These results reflect the potential of R-MnO2 as a photoactive catalyst, being a consequence of presumed photoreduction of Mn4+centers.

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► H2O2 photo-degradation activity of MnO2 is studied by gas pressure monitoring.
► The H2O2 photo-decomposition catalyzed by MnO2 obeys the first order kinetic law.
► The visible light irradiation caused an important increase in the H2O2 decomposition.