Density Functional Theory Study of P-Doped Co₃O₄(111) Facets for HCHO Adsorption: Implications for Metal Oxide Semiconductor Gas Sensors

Volatile organic compounds (VOCs) pose a significant threat to human health, and it is essential to develop advanced VOC gas sensors by understanding the mechanisms. Metal oxide semiconductor gas sensors have the advantages of high sensitivity, high-temperature resistance, stability, and safety. The rational design of crystal facets and doping components can improve the sensing properties. However, the time-consuming experimental optimization of the sensor design has tremendously inhibited the development of the new sensing material. Nevertheless, density functional theory (DFT) calculations shined a light on the fundamental understanding of the sensing mechanism at the molecular level and accelerated the sensor design process. In this study, we used DFT calculations to investigate the sensing properties of the P-doped Co 3 O 4 (111) surface toward methanol, methane, formic acid, water, and formaldehyde. Results showed that P doping changed the surface electronic distribution, increased the charge transfer of HCHO, and enhanced the adsorption energy of other molecules. The significant difference in adsorption energy between H 2 O and HCHO indicates that the P-doped surface exhibits certain antihumidity properties in HCHO sensing. Our work broadens the application of P-doped Co 3 O 4 (111) in the VOC gas-sensing field and provides a theoretical basis for designing metal oxide semiconductor gas sensors.