In this subject area, the aim of our research work is to elaborate protocols for the electrochemical synthesis of materials whether in the form of films or nanostructures.
The field of application for this work is materials for the conversion of energy, particularly those with thermoelectric (TE) properties. To study films' growth mechanisms, the group has developed an in situ measurement bench which couples electrochemical measurement, gravimetric determination and ellipsometric measurement (collaboration with the LCP-A2MC).
This work as a whole can be broken down into three main areas:
The group's previous work which led to the synthesis of n-type films (Bi2-xTe3+x, Bi2Te2,7Se0,3) and p type (Bi0,5Sb1,5Te3) is currently the subject of a technology transfer in association with a major automotive spare parts manufacturer (VALEO) and the French Environment and Energy Management Agency, ADEME. The aim is to create modules on heat exchangers from land motor vehicles with the aim of recovering some of the heat energy that is dissipated.
Among compounds with low dimensionality, thermoelectric nanowires are the subject of a great deal of study as their ZT figure of merit needs to be greatly increased. The first results concerned the electrochemical synthesis of thermoelectric nanowires of bismuth chalcogenides in the pores of a polycarbonate membrane (up to 30 µm in length and 30 nm in diameter). The research covers the control of composition along the full length of nanowires based on the analysis of the electrochemical system's voltamperograms as well as their crystallographic quality. An extension to the ternary compounds Bi1-xSbxTe3 is currently the subject of study.
The high electrochemical stability of ionic liquids (IL) makes them promising electrolytes for doping TE materials with rare earth elements to enhance TE properties. The group's research has shown that ILs can be used to plate materials with metallic lanthanum as a first stage aimed ultimately at obtaining synthesis of Bi2-xLaxTe3. Another feasible way of enhancing the properties of TE materials is by nanostructuring. Recent results have shown that a blend of ILs enables the synthesis of microcrystalline tellurium (Te) nanowires without having to use a porous membrane. The possible synthesis of core-shell Bi-Te type structures from these nanowires is currently being studied.