Isolated nanowires improve heat-to-electricity conversion

Scientists from the University of Warwick, in collaboration with the Universities of Cambridge and Birmingham, have demonstrated how thermoelectric materials – which harvest waste heat and convert it into electricity – could be an important source of renewable energy when shaped into the thinnest possible nanowires. Based on a combination of theoretical and experimental research, they showed that atomically thin nanowires could improve upon the conversion of heat to electricity of their bulk crystalline form, offering unprecedented efficiency.

As described in the journal ACS Nano [Vasylenko et al. ACS Nano (2018) DOI: 10.1021/acsnano.8b02261], waste heat can be converted to electricity more efficiently using one-dimensional nanoscale materials as thin as an atom, potentially leading to a new approach to producing renewable energy from heat-to-electricity conversion. As first author Andrij Vasylenko put it: “In contrast to three-dimensional materials, isolated nanowires conduct less heat and more electricity at the same time.”

“This research demonstrates a viable route for synthesis of novel highly efficient thermoelectric materials"Andrij Vasylenko

With increasing interest in miniaturisation and the improved efficiency of thermoelectrics, nanostructuring holds great promise. Here, the team explored the crystallisation of tin telluride in narrow carbon nanotubes used as templates for the formation of these materials in their lowest dimensional form. They identified a direct dependence between the size of a template and a resulting structure of a nanowire, as well as how the approach can be used to regulate the thermoelectric efficiency. How the electronic conductivity of tin telluride nanowire can be changed from metallic to semiconducting through the appropriate template for synthesis was also displayed, based on protocol that can be applied to a range of materials, allowing the creation of the smallest possible nanowires with highly tuneable properties.

The study could lead to the development of new types of thermoelectric generators, and also greater interest in alternative potential materials for thermoelectrics among abundant and non-toxic chemical elements. As Vasylenko told Materials Today, “This research demonstrates a viable route for synthesis of novel highly efficient thermoelectric materials, but also opens up a possibility for search for thermoelectric candidate materials among abundant and non-toxic elements (in contrast to rare and toxic Tellurium, a basis for all thermoelectrics) that do not demonstrate thermoelectric properties in 3D form”.

As for the next step, the researchers now realise that for the predicted effective thermoelectric properties of tin telluride nanowires to be applied, it will be key to assess the corresponding properties of the compound material, nanowires assembled in bundles, thin films or mats.