A COMPARATIVE-STUDY OF SNO2 AND CROX/SNO2 POWDERS - THEIR MICROSTRUCTURES AND THEIR DIFFERENT RESPONSE TO CO, NO, H2 AND CH4 ATMOSPHERES

Pure SnO2 and CrOx/SnO2 powders with different crystalline sizes have been prepared and characterized by surface-area measurements, TEM measurements, UV-Vis-NIR diffuse reflectance and FT-IR absorption-transmission spectroscopies. The chemical and electronic responses of the samples on interaction with CO, NO, H-2, CH4 at room temperature (RT) have also been studied. The responses are highly affected by the presence of chromium oxide, as revealed by FT-IR measurements. The electronic response to CO and H-2 is lowered and no electronic response is detected for CH4 when chromium oxide is present. The electronic response to NO is enhanced or lowered by the presence of chromium oxide, depending on the thermal pretreatment.