Ni-doped Co3O4 the influence of different exposed crystal facets and doping amount on the humidity sensitivity: Experiment and theory

Highlight • The adsorption characteristics of water and n-butanol molecules on the surface of Co3O4 (1 1 1) and (1 1 0) with different amounts of Ni atoms doping were studied by DFT. • The doping of Ni atoms on Co3O4 can decrease its humidity sensitivity. • After Ni atoms doping on the surface of Co3O4 (1 1 1) and (1 1 0), water molecules` adsorption characteristics on the surface were weakened. • Appropriate Ni doping concentration on the surface of Co3O4 (1 1 1) and (1 1 0) is beneficial for n-butanol sensing. • Minifying humidity sensitivity by doping with Ni atoms on the surface of Co3O4 (1 1 1) and (1 1 0) was verified by both experiment and simulation. Water vapor causes the baseline resistance, response, recovery time, and long-term stability of the metal oxide semiconductor (MOS) gas sensors to change in different humidity. Combining first-principle and experimental can provide an in-depth understanding of the sensing mechanism from the atomic and molecular scales. In this work, we examined the humidity sensitivity of different concentrations of Ni-doped Co3O4 in detail. Co48O64 (1 1 0) and Co48O64(1 1 1) were constructed by HR-TEM and doped with single, double, and treble Ni atoms on both surfaces. We calculated the adsorption of water and n-butanol molecule on these eight surfaces. The results show that Ni doping improves the moisture resistance properties of Co48O64 (1 1 0) and Co48O64(1 1 1), and the sensing properties of C3H9OH adsorbed on Ni2Co46O64 (1 1 0) and Ni2Co46O64(1 1 1) are higher than single and treble Ni atoms doping. To investigate the humidity sensitivity further, we synthesized nanorods Co3O4 with and without Ni doping. The experimental results showed that the humidity sensitivity of Ni-Co3O4 was significantly lower than that of Co3O4. The decrease in the response value for the C3H9OH may be attributed to the change in the concentration of the Ni doping or the difference in the primarily exposed crystal facet.