Pretreatments of Co3O4 at moderate temperature for CO oxidation at −80 °C

Heterogeneous catalysts that can work at ambient temperature are useful for in-door air quality control, pure gas production for fuel cells and semiconductors, gas sensing, and so forth. Deposition of gold nanoparticles on base metal oxide is known to provide highly active catalysts for CO oxidation at temperatures below room temperature. Here we report that some select base metal oxides such as Co3O4, MnO2, and NiO are intrinsically active catalysts for CO oxidation below 50 °C when pretreated at moderate temperature between 150 and 250 °C in a stream of non-reducing dry gases, for example, dry air, CO in air, or N2. These metal oxides are p-type semiconductors and form surface excess oxygen adsorbed at oxygen vacancies which are created by the above pretreatments.

Graphical abstractAmong base metal oxides, Co3O4, MnO2, and NiO were found to be intrinsically very active for CO oxidation, because Co3O4 calcined at 300 °C, for example, could achieve 100% conversion even below −80 °C when pretreated in a stream of non-reducing dry gas between 150 and 250 °C. It was proved that pretreatment in non-reducing dry atmosphere, particularly in N2 and CO/air, at moderate temperatures enhanced the formation of surface oxygen vacancies, where weakly bound molecular oxygen species were formed to react with CO adsorbed on Co3+ site. This finding provides a novel guideline for the creation of base metal oxide catalysts with high activity at low temperatures.Figure optionsDownload full-size imageDownload high-quality image (102 K)Download as PowerPoint slide