Optimization of gas sensing properties ofn-SnO2/p-xCuO sensors for homogenous gases and the sensing mechanism

The gas sensing sensitivity and selectivity are optimized by modulating the concentration ofp-type andn-type materials in n-SnO2/p-xCuO nanocomposites. With the increase ofxvalue, the sensing performance of then-SnO2/p-xCuO composites changed fromn-type top-type. Compared with pristine SnO2, the gas sensing response of SnO2-xCuO (x < 2.78) composites are lower; this can be explained by the opposite gas sensing behavior of SnO(2)and CuO to CO and H-2; CuO in the SnO2-xCuO (x < 2.78) composites will offset the reduction in the resistance of pristine SnO2. Compared other as-prepared SnO2-xCuO (x = 1.00, 2.33, 2.80, 3.00, 4.00) composites, then-SnO2/p-2.78CuO composite (x = 2.78 is the critical value for the p-n transformation) shows the optimal sensing sensitivity and selectivity to CO and H-2. The possible gas sensing mechanism for the optimization of the gas sensing performance ofn-SnO2/p-2.78CuO composite was illustrated based on the results of gas sensing measurement and the results of XRD, TEM, HRTEM, EDS, and XPS characterization. This behavior can be explained by the following reasons, including plenty of p-n heterojunctions formed in the n-SnO2/p-2.78CuO composite, the numerous chemisorbed oxygen on the surface of the composite, and the 6 nm diameter of the nanoparticles.