Enhanced CO Sensing Performances of PdO/WO₃ Determined by Heterojunction Structure under Illumination

The CO sensing performances and mechanism of PdO/WO₃-based sensors were investigated by experiments and density functional theory calculations. The CO sensing performance can be significantly enhanced by decorating WO₃ with PdO, which is attributed to the catalyst (chemical sensitization) and P-N junction (electronic effect). On the one hand, PdO is an excellent catalyst used to promote the adsorption of oxygen species. On the other hand, the constructed P-N junction structure between PdO and WO₃ can facilitate the migration of carriers and suppress the recombination of electrons and holes, which promote the adsorption of more oxygen species. Furthermore, the calculation results verify that decorating WO₃ with PdO can significantly enhance the CO sensing response by providing more adsorption sites available for oxygen species and make more electrons to transfer from CO to PdO/WO₃ configuration. Moreover, the band gap energies of the WO₃ sensor can be reduced by PdO decoration, and the light absorption range in the visible light region can be expanded. More photogenerated electron-hole pairs can be produced based on the P-N junction structure, which can promote the progress of electrochemical reactions. Thus, the PdO/WO₃ material can be a promising candidate to detect CO, and it can effectively utilize the UV-visible light to destruct the CO contaminant.