Enhanced catalytic activity of OMS-2 for carcinogenic benzene elimination by tuning Sr2+ contents in the tunnels.

Cryptomelane-type manganese oxides (OMS-2) have been intensively investigated for application in the catalytic oxidation of carcinogenic benzene, and doping metal ions in the OMS-2 tunnels are widely used for modifying its catalytic activity. In this study, we reported a novel strategy of enhancing catalytic activity of OMS-2 for carcinogenic benzene elimination by tuning Sr2+ concentration in the tunnels. The catalytic activity result revealed that an obvious decrease (△T50 = 27 °C and △T90 = 37 °C) in T50 and T90 (corresponding to benzene conversions at 50 % and 90 %, respectively; initial benzene concentration was 2000 mg m-3; contact time was 1.5 s) had been observed by increasing the Sr2+ concentration in the OMS-2 tunnels. The origin of Sr2+ doping effect on catalytic activity was theoretically and experimentally investigated by CO temperature-programmed reduction, 18O2 isotope labeling, and density functional theory calculations. The result confirmed that increasing Sr2+ concentration in the tunnels not only promoted the lattice oxygen activity, but also facilitated the generation of more oxygen vacancy defects, thus considerably improving the catalytic activity of OMS-2.