Low-temperature CO oxidation over integrated penthorum chinense-like MnCo2O4 arrays anchored on three-dimensional Ni foam with enhanced moisture resistance

Advanced integrated nanoarray (NA) catalysts have been designed by growing metal-doped Co3O4 arrays on nickel foam with robust adhesion. Ternary MCo2O4 NA catalysts were prepared by doping urchin-like Co3O4 with different transition metals (Cu2+, Mn2+, Fe2+, Ni2+, Zn2+, Fe3+ and Al3+). These catalysts exhibited novel morphologies and can be directly applied as monolithic materials for CO oxidation. Among the MCo2O4 NA catalysts, CuCo2O4 nanoneedles manifested the highest catalytic activity in dry air, achieving an efficient 100% CO oxidation conversion of 20000 h(-1) at 146 degrees C, due to its reducibility at lower temperature, lattice distortion of the spinel structure, and abundant surface-adsorbed oxygen (O-ads). The doped catalytic systems were further optimized by controlling the volume ratio of reactive components in the mixed solvent, the Cu or Mn contents to determine excellent catalysts for direct application to CO oxidation at 1.0 vol% moisture. Penthorum chinense-like MnCo2O4 NAs showed optimal catalytic performance at 1 vol% moisture (T-100 = 175 degrees C), with activity higher than that of the CuCo2O4 NA catalyst, indicating that the synergistic effect between MnOx and Co3O4 improved the moisture resistance and stability. It was concluded that the moisture resistance provided by introducing active sites on Co-based catalysts decreased as follows: Mn sites > Co sites > Cu sites > Ni sites. MCo2O4 NAs, with predominantly exposed {110} surfaces, showed higher catalytic activity than catalysts with exposed {111} surfaces. This study suggests that the as-prepared MnCo2O4 NAs anchored on 3D Ni foam with remarkable moisture resistance have potential applications in CO oxidation.