Volatile organic compounds (VOCs) are organic molecules with high vapor pressure at room temperature. While some of them are innocuous substances such as aroma compounds, many are harmful to health and environment. These VOCs are classified as air pollutants. A possible approach to reduce the amount of VOCs in air is catalytic oxidation, however, this method needs highly efficient catalysts.

Junhua Li and colleagues, Tsinghua University, Beijing, China, have developed hierarchical core–shell Al₂O₃@Pd-CoAlO microspheres which can catalyze the oxidation of the VOC toluene to carbon dioxide and water. The team started with AlOOH microspheres, on which CoAl layered double hydroxides (LDHs) were grown. Palladium nanoparticles were synthesized in situ and immobilized on the microspheres by mixing the spheres with an aqueuos solution of Na₂Cl₄. They were then calcined at 600 °C in air to give the final oxide species.

The approach combines the high catalytic efficiency of supported palladium catalysts with the stability and high surface area of Al₂O₃. The microspheres showed outstanding catalytic efficiency, making them promising candidates for toluene combustion.

• Hierarchical Core–Shell Al₂O₃@Pd-CoAlO Microspheres for Low-Temperature Toluene Combustion,
  Shen Zhao, Fangyun Hu, Junhua Li,
  ACS Catal. 2016.
  DOI: 10.1021/acscatal.6b00144