Nanostructured Multifunctionnal Electrodes (NAMUEL) – ENaMU

The present project aims at the fundamental understanding of NAnocomposites MUltifunctionnal ELectrodes (NAMUEL) made of electronically conducting polymers (ECP) or pi-conjugated oligomers with aligned carbon nanotubes (CNT). Among the numerous possible applications, these NAMUEL will be studied mainly through their electrochemical properties, in supercapacitor configuration but several applications, like solid state dye-sensitized solar cells, electrochemical sensors or CO2 storage are possible with such nanomaterials. These applications are of importance nowadays in term of energy conversion saving or storage, environmental health.

Supercapacitors and photovoltaics will be mainly studied in this project since the LPPI has a strong experience in these two fields. Concerning electrochemical sensors, this field is emerging in the laboratory since 2 years and the nanocomposites will be studied as possible electrode materials. In the case of CO2 storage, the potentialities of NAMUEL will be ‘only’ estimated as possible future development.

Concerning supercapacitors, some major drawbacks of the ECP (their limited electrochemical cyclability, short-time stability) and of the CNT (fabrication costs, health risk) are usually presented as deep technological brakes for their possible commercial development. For these reasons, there is no strong demand from industry actually for the development of such hybrid nanomaterials. For example, at this time industry requires supercapacitors as energy or power supply components (batteries replacement, stationary power systems…). Then supercapacitors made from ECP are not yet enough attractive due to their low performance in term of cyclability compared to existing solutions like porous carbon powder components. Nevertheless, the emergence of room temperature ionic liquids (RTIL) offers new perspectives to improve these materials. Then, in combination with the large CNT specific area (ca. 50m²/g) the nanocomposites ECP/CNT become more attractive. Moreover, supercapacitors made with ECP and CNT may be used as micro-power sources (µ-supercapacitors) in organic electronic systems. Indeed, one of the main innovative advantages of ECP/CNT nanohybrids is the possibility to reach higher current densities and frequencies of charge/discharge cycles. For that, the nanocomposites require a deep control of their morphology and the thickness of the ECP onto the CNT as well as a fine control of the CNT purity, density, thickness and alignment. These points will be largely developed in this project not only for supercapacitors applications, but also for the others mentioned above because these nanocomposites electrodes have versatile employments.

For photovoltaïc devices, the nanocomposite offers an interesting possibility to elaborate a TiO2/Dye||ECP/CNT cell that can improve the conversion efficiency compared to existing systems (solid-Graetzel cells, conversion~1-3%). The hole transport will occur in an optimized thin solid layer, so that the undesired recombination’s probabilities will be as low as possible.

For electrochemical sensors, these nanocomposites afford a convenient way to increase the number of interaction sites of the analyte at the surface of the electrode. For example, electrochemical sensors are less sensitive if the electrode area is small. Reducing their area (example in the field of biology with micro-electrodes) must be compensated by porous electrodes. Development of detection µ-systems requires the use of smaller electrodes (at the µ-level scale) like the nanocomposite electrode we mean to fabricate.

For CO2 storage, it is important to improve the density of active sites able to store CO2. NAMUEL may be appropriate candidates in such application. However, the storage capacity will be ‘only’ evaluated through some experiments with a collaborator