Highly enhanced thermoelectric performance of copper sulfide by compositing with CNT & CuO

Abstract

Copper Sulfide as a type of environmentally friendly and low-cost thermoelectric material has attracted extensive attention in the last few years. However, the thermoelectric performance and stability of pristine copper sulfides are poor because of the excessive hole concentration and Cu-ion migration behavior in the high temperature, which are the key reason why this material system can’t become the candidate of commercial application. In this paper, carbon nanotubes (CNTs) were coated with CuO by ultrasonic spraying pyrolysis, and then waiting to be compounded with Cu1.8S material. A series of copper sulfide-based composites were produced by combining with solid-state reaction (SSR) and spark plasma sintering (SPS) technique. The effect of dispersing CNT/CuO on optimizing thermoelectric properties of copper sulfide was investigated in detail in the temperature range from 323 K to 773 K. Carrier concentration of copper sulfides was tuned by carefully regulating Cu vacancies, resulting in the significantly improved Seebeck coefficient. Meanwhile, the thermal conductivity was drastically decreased owing to the introduced pores and weakened contribution from electrical conductivity. A maximum thermoelectric figure of merit (ZT) value of 1.05 was obtained at 773 K for the copper sulfide-based bulk composite, namely Cu1.8S-5 wt.% CNT/CuO, which was twice as higher as the pristine Cu1.8S specimen. This bulk composite also exhibits a relatively stable thermoelectric performance in the cycling test.