Graphene network in copper sulfide leading to enhanced thermoelectric properties and thermal stability

Copper sulfide has received wide attention as a potential thermoelectric material with high performance and abundant resource. While the liquid-like Cu ions play an important role for the low kappa(L) and high ZT values, grain-boundary engineering is needed to further enhance the phonon scattering and the thermal stability of Cu2-xS. Here, we introduced the 3D graphene heterointerface into the Cu2-xS matrix by a facile technique combining mechanical alloying (MA) and spark plasma sintering (SPS). A significant ZT enhancement was realized with the highest ZT up to 1.56 and a high power factor of 1197 mu Wm(-1) K-2 at 873 K in the sample with 0.75 wt% graphene. Additionally, the composite showed excellent reproducibility of PF after five cycles testing from room temperature to 873 K, which confirmed the practical application potentiality of this composite.