Enhanced thermoelectric performance based on special micro-configuration of graphene-ZnO induced by high-pressure and high-temperature

Zinc oxide (ZnO) is a promising high-temperature thermoelectric material. Graphene is typically a two-dimensional material, and its development and application have attracted wide attention due to its excellent thermal stability and mechanical properties. To the best of our knowledge, the graphene-ZnO (C–ZnO) composite has never been studied in the field of thermoelectric conversion. The high-pressure and high-temperature (HPHT) technique has unique advantages in improving the thermoelectric properties of ZnO. In this study, for the first time, C–ZnO bulk energy materials with novel micro-configuration were prepared by rapid sintering using the HPHT method. Observation under a microscope revealed that as the doping amount of graphene increased, a large number of graphene nanowires formed connected between the ZnO grains, and with the excess amount of graphene introduced the morphology of the ZnO grains changed and their size became smaller. This novel micro-configuration of the 0.1C–ZnO sample showed an ultrahigh electrical conductivity of 2.8 × 104 S/m with a significantly lower lattice thermal conductivity of 4.3 Wm−1K−1 at 973 K. Ultimately, at 973 K, the zT value of the 0.1C–ZnO sample was 129 times higher than that of pure ZnO. Therefore, the high-temperature thermoelectric material C–ZnO prepared by the HPHT method can be used in automobile exhaust systems and industrial boilers to effectively recover and reuse the waste heat.