Influence of CuO doping on cobalt oxide for thermochemical energy storage

Thermochemical energy storage (TCS) was considered as a promising candidate for renewable energy utilization and energy efficient utilization. Particularly, metal oxide-based TCS has attracted increasing attention due to its operation possibility with air. In this work, CuO-doped cobalt oxide composite was prepared by a simple me-chanical mixing process and explored for TCS application. The influences of CuO doping on the redox behavior, repeatability and the optical absorption property of cobalt oxide were investigated. Doping with CuO signifi-cantly decreased the onset temperature of reduction by 60 degrees C compared to pure cobalt oxide. Meanwhile, the result verifies that the onset temperature of re-oxidation could be tuned in the range from 825 to 890 degrees C by altering the doping amount of CuO. The reason for the tunable onset temperature was examined from the viewpoint of the structural transformation of the composite during the reduction/re-oxidation process. It was presumed that the doping amount of Cu species in CoO might relate to the onset temperature of re-oxidation. The repeatability of the composite was highly affected by the doping amount of CuO. Moreover, CuO with relatively small particle size exhibited a positive effect on improving the repeatability of CuO-doped cobalt oxide com-posite. Additionally, the absorption spectra demonstrate that CuO doping would affect the optical absorption property of the composite, enhancing the absorption of visible light. Hence, the results obtained in this work indicate that doping with CuO could be a promising method to extend the applicability of cobalt oxide-based system for TCS application.