Acetone sensing mechanism of PdO-modified hexagonal WO3 (001) surface: DFT calculations

DFT calculations are used to investigate the acetone sensing mechanism of PdO-modified hexagonal WO3 (001) surface. It is concluded that compared to the pure h-WO3 (001) surface, modifying the surface with PdO could increase the available adsorption sites for acetone and leads to a sharp increase in the amount of charge transferred from acetone to the surface of the material, which contributes to a decrease in the resistance of hWO(3) (n-type semiconductor material). Moreover, we found that the oxygen concentration and experimental temperature have significant effects on the acetone sensitivity of the PdO-modified h-WO3 (001) surface. In an anoxic environment, the O originating from acetone easily adsorbs on a W or Pd site. With increasing temperature, acetone desorbs from the material, explaining the optimal operating temperature of h-WO3 sensors for acetone observed in experiments. Moreover, in oxygen-rich environments, some intermediate products were generated, which suggests an alternative consideration for the interpretation of acetone sensing mechanism.