Theory-guided oxygen-vacancy for enhancing H2S sensing performance of NiO

As a stable and promising metal oxide semiconductor, NiO has been developed in gas-sensing field. However, the low sensitivity of p-type semiconductor metal oxides hinders their wide application in the sensing field. Herein, we report the introduction of oxygen vacancies into NiO to adjust its electronic structure and adsorption energies for H2S, HS, S, and H species. The corresponding theoretical results indicate that the oxygen vacancies acted as unsaturated and active sites can directly change the electronic structure of NiO and further enhance the sensing performances of H2S by decreasing the transition state energy barriers of H2S and HS species respectively dissociated into HS/H species and S/H species on the surface of NiO. Subsequently, the sensing experiments and ex-situ XPS analysis reveal the enhanced H2S sensing mechanism of NiO by introducing oxygen vacancies. In general, the sensing characteristics and sensing mechanism of NiO for H2S were systematically studied through theoretical calculations and experimental phenomena. This work will promote the development of design of oxygen vacancy in MOS sensors and provide new way for revealing the sensing mechanism.