Enhanced Toluene Combustion over Cryptomelane Catalysts: Influence of Cu Doping on Physicochemical Properties and Catalytic Performance

The catalytic combustion of toluene over cryptomelane and Cu-doped cryptomelane catalysts was investigated to evaluate the effect of copper incorporation on catalytic performance. It was found that a small addition of Cu into the cryptomelane framework resulted in a notable decrease in the temperature of 90% toluene conversion. To elucidate the structure-activity relationship, the catalysts were comprehensively characterized using XRD, FTIR, SEM-EDS, N₂ physisorption, XRF, XPS, O₂-TPD, and H₂-TPR techniques. The results revealed that Cu doping modifies the physicochemical properties of cryptomelane, most importantly the share of lattice and surface oxygen species, enhancing redox behavior and oxygen mobility, which in turn improves catalytic activity. For the lowest dose of Cu, both the temperatures of 50 and 90% conversion were found to be lowest among investigated catalyst series: 180 and 195 °C, respectively. These findings highlight the potential of Cu-doped cryptomelane as an efficient catalyst for the abatement of volatile organic compounds.