Synthesis and enhanced room-temperature thermoelectric properties of CuO–MWCNT hybrid nanostructured composites

Abstract

This work presents the synthesis of novel copper oxide–multiwalled carbon nanotube (CuO–MWCNT) hybrid nanostructured composites and a systematic study of their thermoelectric performance at near-room temperatures as a function of MWCNT wt% in the composite. The CuO–MWCNT hybrid nanostructured composites were synthesized by thermal oxidation of a thin metallic Cu layer pre-deposited on the MWCNT network. This resulted in the complete incorporation of MWCNTs in the nanostructured CuO matrix. The thermoelectric properties of the fabricated CuO–MWCNT composites were compared with the properties of CuO–MWCNT networks prepared by mechanical mixing and with the properties of previously reported thermoelectric [CuO]_99.9[SWCNT]_0.1 composites. CuO–MWCNT hybrid composites containing MWCNTs below 5 wt% showed an increase in the room-temperature thermoelectric power factor (PF) by ∼2 times compared with a bare CuO nanostructured reference thin film, by 5–50 times compared to mixed CuO–MWCNT networks, and by ∼10 times the PF of [CuO]_99.9[SWCNT]_0.1. The improvement of the PF was attributed to the changes in charge carrier concentration and mobility due to the processes occurring at the large-area CuO–MWCNT interfaces. The Seebeck coefficient and PF reached by the CuO–MWCNT hybrid nanostructured composites were 688 μV K⁻¹ and ∼4 μW m⁻¹ K⁻², which exceeded the recently reported values for similar composites based on MWCNTs and the best near-room temperature inorganic thermoelectric materials such as bismuth and antimony chalcogenides and highlighted the potential of CuO–MWCNT hybrid nanostructured composites for applications related to low-grade waste heat harvesting and conversion to useable electricity.