Control of Electrical and Thermal Transport Properties by Hybridization of Two-Dimensional Tungsten Disulfide and Reduced Graphene Oxide for Thermoelectric Applications

Thermoelectric efficiency is determined by the figure of merit (ZT) with the achievement of high electrical conductivity (sigma), high Seebeck coefficient (S), and low thermal conductivity (k) for high performance thermoelectric devices. Tungsten disulfide (WS2) has been reported to have a comparably high S (3.5 x 10(2)similar to 9.5 x 10(2) mu V/K) and low sigma (10(-2)-10(-1) S/m), which leads to a low ZT value (approximately 0). In this study, WS2 particles were hybridized with highly conductive reduced graphene oxide (rGO) particles (similar to 10(5) S/m). The inclusion of rGO provides conductive paths for the transfer of carriers in the composites, and thus, this led to an increase in sigma (similar to 3 x 10(3) S/m). The hybrid material of WS2/rGO, as a function of the weight percentage of rGO, was fabricated by spark plasma sintering. As a result, the power factor in a WS2/0.8 wt % rGO (87 mu W/mK(2)) with enhanced sigma was 310% greater than that of WS2. Moreover, two-dimensional structures of the materials contributed to the induction of phonon scattering and resulted in steady k in spite of enhanced sigma with increased rGO content. Consequently, an optimized ZT value was obtained for the WS2/0.8 wt % rGO sample; this value was 260% greater (approximately 6.8 x 10(-4)) than that of WS2 without rGO (approximately 1.9 x 10(-4)).