Doubly ionized oxygen vacancies dominated Co3O4 nanoparticles for highly selective NH3 sensing application at room temperature

In this work, polycrystalline Co 3 O 4 nanoparticles rich in doubly ionized oxygen vacancies (V O ¨) exhibit superior NH 3 sensing performance at room temperature. Adjusting charge states of oxygen vacancy has been extended to p-type metal oxide (Co 3 O 4 ) for the first time. • Polycrystalline Co 3 O 4 nanoparticles are synthesized by hydrothermal-calcination. • Co 3 O 4 is rich in oxygen vacancy mainly with doubly positive charges (V O ¨). • Co 3 O 4 exhibits excellent performance for NH 3 sensing at room temperature. • Adjusting charge states of V O has been extended to p-type metal oxide (Co 3 O 4 ) for the first time. • Enhanced sensitivity is attributed to high content of Co 3+ and V O ¨. Polycrystalline Co 3 O 4 nanoparticles were synthesized using a hydrothermal method with calcination. The microstructure and surface defects of these materials were investigated systematically. Room temperature gas sensing properties of Co 3 O 4 nanoparticles were tested towards ammonia (NH 3 ). The response value of Co 3 O 4 -2 h gas sensor to 200 ppm NH 3 is 102.8 with response and recovery time of 65 s and 208 s, respectively. The Co 3 O 4 -2 h sensor also exhibited high selectivity, good repeatability and long-term stability. After excluding the impact of specific surface area and grain-size effect on sensitivity, the boosted sensing performance of Co 3 O 4 -2 h nanoparticles is mainly attributed to the high Co 3+ concentration and the abundant doubly ionized oxygen vacancies (V O ¨). This work provides a promising strategy to enhance gas sensing properties of p-type oxides by adjusting charge states of oxygen vacancy.