Catalytic oxidation and selective sensing of carbon monoxide for sense and shoot device using ZnO–CuO hybrids

Abstract In the present work, we have demonstrated that ZnO–CuO based hetero-composites exhibit selective CO sensing with T 100 is in close proximity to T opt to yield simultaneous CO sensing together with its 100% catalytic oxidation for sense and shoot devices. When these heterocomposites are exposed to CO, reduction of Cu 2+ ions in CuO grains leads to a strong metal semiconductor interaction (SMSI) between Cu 2+ /Cu + /Cu 0 species (in CuO grains) and ZnO grains across the ZnO-CuO interface. The SMSI interaction promotes the generation of oxygen vacancies in neighboring ZnO lattice. Eventually activated oxygen (O* ads ) and CO (CO* ads ) are preferentially chemisorbed on zinc oxide (in its vacant oxygen sites) and CuO (on the surface of Cu 2+ /Cu + /Cu 0 ions) respectively. The activated oxygen reacts immediately with adsorbed CO to yield selective CO sensing together with 100% CO oxidation. For ZnO–CuO (1:1) composites, the measured T opt (∼175 °C) and T 100 (∼200 °C) temperatures are significantly lowered as compared to the respective temperatures measured for indium doped ZnO (T opt ∼300 °C, T 100 ∼550 °C) and CuO (T opt ∼200 °C,T 100 ∼300 °C) catalysts. Fine tuning of the mole fraction of ZnO and CuO are necessary for these hetero-composites to yield T 100 of catalytic activity close to T opt for maximum CO sensing.