Sonochemical Synthesis of Biobased Composite Materials for Energy Applications

Project leaders

Andrea Sorrentino, David Velayutham

Agreement

INDIA - CSIR-expired - Council of Scientific and Industrial Research

Call

CNR-CSIR 2016-2018

Department

Chemical sciences and materials technology

Thematic area

Chemical sciences and materials technology

Status of the project

New

Research proposal

Dye Sensitized Solar Cells (DSSC) has attracted much attention, due to their easy fabrication, flexibility, low production cost and high efficiency. A DSSC is composed of two transparent electrodes and a mesoporous layer of titanium dioxide (TiO2) nanoparticles, covered with a molecular dye that absorbs sunlight. The titanium dioxide is immersed under an electrolyte solution, above which is a platinum-based catalyst. Sunlight passes through the transparent electrode into the dye layer where it can excite electrons that then flow into the titanium dioxide. The electrons flow toward the transparent electrode where they are collected for powering a load.
The electrolyte is one of the key ingredients; it provides internal electric conductivity by diffusing within the mesoporous TiO2 layer and is an important factor in determining the cell performance. Even if the light to electrical energy conversion efficiencies of DSSCs based on liquid electrolytes is quite high, they present several problems, such as leakage and volatilization of the liquid, possible desorption and photo degradation of the attached dyes, and the corrosion of the counter electrode. These problems create difficulties in cell fabrication and limited the long term performance and practical use of these DSSC. To prevent or reduce these problems, several methods have been introduced. Among them, Gel polymer electrolyte (GPEs) which possess both cohesive properties of solids and the diffusive property liquids, are the most interesting. Due to this unique characteristic, GPEs presents several advantages, such as low vapor pressure, excellent contacting and filling properties between the nano structured electrode and counter electrode, higher ionic conductivity and excellent thermal stability. During the last decades, new types of GPEs based on natural polymers (like cellulose acetate, starch, gelatin, chitosan and biodegradable synthetic polymer such as polyvinyl alcohol and polycaprolactone) have been proposed due to their biodegradability, availability and low production cost. In spite of these advantages, the commercial application of these materials as electrolytes has been delayed because of their tendency to crystallize and their lower ionic conductivity. A possible solution for these drawbacks is represented by the room temperature ionic liquids (RTILs). They are a new class of salts that are liquid at room temperature and can simultaneously dissolve organic and inorganic substances. Compared to conventional organic solvents, RTILs present a number of advantages such as wide liquid phase range, non-flammability and very low vapor pressure at room temperature. They are also being considered as "green solvents" for various separation processes. When added to a polymer, RTILs increase the ion mobility and plasticize the matrix by transforming the crystalline domain into amorphous phase. The unique properties of RTILs are determined by their structure and interaction of ions in the melt. Since there is virtually no limit in the number of RTILs that can be synthesized, it is possibility to design a solvent with the necessary properties for a specific application. In particular, the choice of base cation and anion creates the major properties whereas the fine tuning of properties is possible by the variation of the length and branching of the alkyl groups incorporated into the cation.
The aim of this research is to synthesize a new generation biodegradable RTIL-GPE materials by utilizing low cost, bio based materials. Particular attention will be devoted to the development of a sustainability transformation process by minimizing the use of solvent, time, energy and hazardous materials. The materials obtained will be accurately characterized in terms of infrared spectroscopy (IR), electrochemical impedance spectroscopy, cyclic voltammetry, thermo gravimetric analysis (TGA), Rheology and thermo mechanical analysis (DTMA). Finally, these materials will be tested as gel polymer electrolytes in DSSC device and thus characterized in terms of cell efficiency, Short circuit current (Isc), Open circuit voltage (Voc) and Fill factor (ff).
The Indian group has experience in the sonochemical production of metallic, bimetallic and core-shell nanoparticles and metal loaded semiconductor nanoparticles. On the other hand, the Italian group has a long experience working in mechanochemical synthesis of polymer material and nanocomposites, development of functional polymer materials for barrier and electrical applications. In addition, this group uses rheological and spectroscopic techniques for the characterization of polymer materials obtaining information related to structure and morphology. These characterization are complementary to the spectro-electrochemical experiments (carried out by the Indian group) to obtain valuable information about the interphase solution/oxide under working conditions.
The collaboration between the two groups will provide a better knowledge about controlled production of different nanostructures, and especially of thin polymer films. The obtained material and the process developed during the project activity will provide a clear picture on the possibility to use bio-based composites materials in different advanced applications. In this sense, both groups also complement each other, as the Indian group is more focused in environmental applications (using metal oxide nano powders), while the Italian group works in energetic related topics (using polymer-carbonaceous filler as conducting and energy storage materials).
Benefits for each country:
(i) Spread the obtained results by peer-reviewed joint-papers in specialized journals.
(ii) Spread the obtained results by joint-contributions to International and National Meetings
(iii) Supervision of, at least, two Ph.D. thesis (one per group) along with the corresponding master projects
(iiii) Development of a new reactor for checking the developed materials

Research goals

The main objectives of this proposal are to:
(1) Design and development of a new family of eco-friendly gel polymer composite for energy applications
(2) Development of a new transformation process based on low-cost, sustainable techniques
(3) Assembly and testing of small modules Solar Cells based on the previous gel polymer composites

The project will be developed by following five interconnected steps, in order to optimize the collaboration between both laboratories. Firstly, will be to define the material properties and morphology to be obtained by the selected gel polymer system. Secondly, will be design and development of the experimental route for the material synthesis. Thirdly, the as-prepared materials will be characterized in terms of composition, morphology, structure and electro-chemical impedance spectroscopy. The results obtained will be useful for a scale-up of the process with a relative optimization of the synthesis procedure. Finally, the materials with the best performances will be used for prepare a DSSC that will be characterized in terms of efficiency and durability. Based on this specific approach, the research program will be divided in the following work packages:

WP1: Material selection (WP-leader all groups)
WP2: Material synthesis (WP-leader India group)
WP3: Material characterization (WP-leader Italian group)
WP4: Process optimization (WP-leader Italian group)
WP5: DSSC assembly and characterization (WP-leader India group)

Last update: 19/05/2025