Synergistic Ni single atoms and oxygen vacancies on SnO 2 nanorods toward promoting SO 2 gas sensing

Monitoring sulfur dioxide (SO 2 ) in the environment requires a sensor to feature adequate sensitivity, selectivity, and low detection levels. Herein, we report an ultrasensitive, low-concentration SO 2 gas sensor that employs single atoms nickel anchored on oxygen vacancy-rich SnO 2 nanorods (SAC-Ni/H-SnO 2 ) as the sensing material. The response value of the SAC-Ni/H-SnO 2 sensor to 20 ppm SO 2 is 48, and the detection limit is 100 ppb, which is superior to most of reported SO 2 sensors. In-situ DRIFTS and ESR characterization shows that the coupling effects of SAC-Ni and adjacent oxygen vacancy on SnO 2 surface, which promote the adsorption of SO 2 and activation of chemisorbed oxygen, respectively. This effective single-atom catalyst provides a new insight into complex gas sensing mechanisms and demonstrates a promising approach of using single-atom catalysts for gas sensing applications.