The catalytic performance of ultrasonically prepared CuxCo3−xO4 catalysts towards CO oxidation at relatively low temperature

Abstract

A series of CuxCo3−xO4 catalysts were prepared and presented as active and stable catalysts in the oxidation of CO into CO2 at relatively low temperatures. These nanoparticles were synthesized by co-precipitation assisted ultrasonic radiation method. The thermal behavior, structural, spectroscopic, texture, and morphological characterizations were carried out adopting TG-DTA, XRD, XPS, FTIR, N2-sorption, and TEM techniques. In addition, electrical conductivity and surface chemisorbed oxygen measurements were also studied. The quantity and strength of basic sites were estimated using CO2-TPD. The results revealed that the insertion of Cu2+ with values of x from 0.25 to 0.75, into Co3O4 catalysts calcined at 400 °C monotonically increases the SBET, the amount of surface chemisorbed oxygen, catalyst basicity, electrical conductivity and catalytic activity. In addition, the activity increases to an optimal amount of Cu2+ substitution for Co2+ with x = 0.75 which exhibited the most active catalyst with a value of T100 of 125 °C. Results of CO2-TPD demonstrated that, incorporation of Cu2+ with a value of x of 0.75 not only increases the total basicity, but also altered strength and distribution of basic sites over the surface of the catalyst. The role of the active redox sites existed on the surface of these catalysts such as, Co3+/Co2+, Cu2+/Cu+ and Co3+/Cu+, which are accountable for such alteration, was also debated. The most active catalyst Cu0.75Co2.25O4 displayed a long-term stability up to 100 h.