Regulating microscopic surfaces and structures to boost n-butanol sensing performances in NiCo2O4/NiO composites

Abstract

Transforming gas sensing materials from having no performance to presenting high sensing selectivity is full of challenges. For this purpose, water bath assisted sodium borohydride (NaBH₄) treatment is developed and is employed to boost gas sensing dynamics of spinel structure NiCo₂O₄ microspheres. The n-butanol recognition, gas adsorption and carrier transport in the sensing process are tremendously optimized by etching crystal surfaces, breaking metal oxygen bonds, increasing surface area, enhancing oxygen vacancies and dislocation density, reducing crystallite size as well as forming NiCo₂O₄/NiO heterojunction. The NiCo₂O₄ microspheres treated by 0.5 M NaBH₄ solution (NCO-0.5) present apparent n-butanol gas response and sensing selectivity compared to the untreated NiCo₂O₄ microspheres without sensing performance. The density functional theory (DFT) calculation based on adsorption energy and charge density difference further validates the evident adsorption interaction and charge transfer between heterojunction microspheres and n-butanol gas. This feasible NaBH₄ treatment strategy provides more possibilities and choices for performance improvement of semiconductor gas sensing materials.