Bismuthene nanosheets prepared by an environmentally friendly method and their thermoelectric epoxy nanocomposites

Theoretical research has predicted high thermoelectric performance for bismuthene nanosheets, but it is a great challenge to prepare these nanosheets due to low efficiency and intensive oxidation. We herein report an efficient, environmentally friendly preparation method for bismuthene nanosheets, each being 1–1.5 nm thick in average, through mechanochemical treatment with an ethanol system. The system was found to prevent adverse oxidation in comparison with a pure water system. Although neither the oxidation reactions nor the exfoliation could significantly change the Seebeck coefficient of bismuthene nanosheets, their power factor was measured as 155.6 ± 15.4 μW·m^-1K^-2. An epoxy nanocomposite was prepared containing 99 vol% of bismuthene nanosheets, to create a thermoelectric generator. It converted a temperature gradient of 11°C generated by human body into an electrical output of 18.62 nW. Our mechanochemical exfoliation method for the preparation of low-oxidation bismuth nanosheets offers insights for large-scale fabrication of nanosheets and their composites for industrial applications. It advances the field of thermoelectric nanocomposites.