Porous Mn-doped Co3O4 nanosheets: Gas sensing performance and interfacial mechanism investigation with In situ DRIFTS

Unraveling the gas-solid interfacial sensing mechanism during gas sensing is very essential for the development of high-performance gas sensors. In this work, the Mn-doped Co3O4 porous nanosheets with 5.6 times higher response than pristine Co3O4 and short response/recovery time (55/30 s) for 100 ppm toluene gas is synthesized. More importantly, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is conducted to investigate the gas-solid interfacial sensing mechanism over 3-Mn-Co3O4. The interfacial reaction species have been monitored, such as methylbenzene, benzyl alcohol, benzaldehyde, benzoic acid, carbon monoxide, and water molecule. These species originate from the elementary and overall reactions during toluene gas sensing. The dynamic evolution of surface species could be divided into three stages of adsorption reaction, reaction balance, and desorption reaction. Furthermore, combined with the density function theory simulation calculation, the gas-solid interfacial sensing mechanism over 3-Mn-Co3O4 is proposed. Toluene molecule reacts with the surface active oxygen species resulting in the occurrence of a series of elementary reactions and the generation of intermediates. The products of overall reaction are CO2 and H2O during gas sensing. Our work implements a meaningful exploration of in situ DRIFTS in gas-sensing field and provides a distinctive view to understand the gas-soild interfacial gas-sensing mechanism.