Enormous enhancement of Pt/SnO2 sensors response and selectivity by their reduction, to CO in automotive exhaust gas pollutants including CO, NOx and C3H8

Cheap sensors are necessary for detection of automotive exhaust gas pollutants, to diagnose the fuel injector, engine and catalytic converter performances. SnO2 and Pt/SnO2 sensors reduced in CO were used for highly sensitive and selective detection of CO as the major pollutant in automotive exhaust gases. SnO2 was prepared by a sol-gel method, on which Pt nanoparticles were deposited by an impregnation method. The sensors were reduced in 1%CO in Ar at 300, 400 and 500 degrees C for 1.5 h and characterized by Raman, TEM, HR-TEM, XRD, and BET methods. The responses of the sensors to CO, C3H8 and NOx as the main automotive exhaust gas pollutants were measured in an automated continuous-flow system. The SnO2 and Pt/SnO2 transient reductions by CO, which oxidises to CO2 using SnO2 lattice oxygen, are studied at 400 degrees C. The formation of SnO by the reduction is significantly enhanced for the Pt/SnO2 sample. As compared to the Pt/SnO2 sample calcined in air, the reduced Pt/SnO2 sample exhibits up to 125 fold higher stable responses to CO, greater selectivities of 1758 and 4071 to CO relative to C3H8 and NO, respectively. This is explained by the formation of SnO-SnO2 p-n junction.