Electrochemistry is a study of the correlation between applied or measured electrical potential and corresponding chemical changes, or vice versa. Different voltammetry techniques have been developed to measure the potential, charge or current of electrochemical systems for analytical and characterization purposes. I have been employed several voltammetry techniques such as cyclic voltammetry, square wave voltammetry, chronopotentiometry as well as electrochemical impedance spectroscopy (EIS) to obtain a clear insight into the interfacial electrochemical behavior between the designed electrode and electrolytes. Particularly, I use cyclic square wave voltammetry method to study the mechanism of electron transfer of electroactive materials in different electrode/electrolyte interfaces.
Supercapacitors also known as electrochemical capacitors are types of rechargeable electrical energy storage devices with much high power density compared to regular rechargeable batteries and extremely higher energy density compared to conventional capacitors. Their fast charge/discharge feature along with their long cycle life makes them a promising candidate for being used as a primary energy storage system in portable electronic devices and hybrid vehicles. However, their lower energy density compared to commercial Li-ion batteries is an issue that hinders their widespread applications; therefore they have been mainly employed in short-term power boosts, such as emergency power supplies and peak power assistance for batteries in electric vehicles where high power density is required.
It is highly desirable to increase the energy density of supercapacitors to approach that of batteries, which could enable their use as a primary power source. I addressed this challenge in my M.Sc. research by designing graphene aerogel-based nanocomposites with high surface area as an electrode material for supercapacitors. I modified graphene aerogel sheets by small molecule to minimize their aggregation that happens due to the existence of pi-pi interaction between graphene sheets. In this project which involved a lot of electrochemistry and solid-state materials characterization, I could design different types of functionalized nanocomposites with large pore sizes and enhanced capacitance. I learn that the large pores maximize and facilitate electrolyte accessibility to the electrode and results in improved supercapacitve performance. This was a small step towards increasing the energy density of supercapaitors and making them more applicable as primary energy storage systems, however, materials science and the supercapacitor community still need a brilliant idea or discovery to revolutionize the rechargeable energy storage systems.
Electrosynthesis of redo-ox active materials for energy storage applications
Electrochemistry is more than a characterization tool and it can be employed for the synthesis and deposition of metal/metal oxide nanoparticles as well as conductive polymers. The reaction is conducted at the interface of the electrode and electrolyte and controlled by applying a current or voltage. The size, morphology, thickness of the deposited materials can be readily controlled by the applied current. Therefore, electrosynthesis is a much simpler, cost-effective, controllable, and consequently scalable method compared to conventional wet synthetic methods. Using electrosynthesis, particularly cathodic electrodeposition I have synthesized polyaniline, polypyrrole, and metal oxide nanoparticles such as Co(OH)2, Ni(OH)2, ZnO, and Fe2O3 on conductive substrates for being used as electrode materials in supercapacitors. Below are the scanning microscopy images of the synthesized Co(OH)2 and Ni(OH)2 nanoparticles that were synthesized in 2 minutes during the electrosynthesis. I believe in the power of electrochemistry for creating high-performance and cost-effective materials for application in sensors and energy storage devices.
1. Electrochemical investigation of functionalized graphene aerogel with different amounts of p-phenylenediamine as an advanced electrode material for supercapacitors, Materials research express, 2016,03, 075501, https://iopscience.iop.org/article/10.1088/2053-1591/3/7/075501/pdf.
Habib Gholipour-Ranjbar, Mohammad Reza Ganjali, Parviz Norouzi, Hamid Reza Naderi.
2. Synthesis of cross-linked graphene aerogel/Fe 2 O 3 nanocomposite with enhanced supercapacitive performance, Ceramics International,2016,42,12097–12104, https://doi.org/10.1016/j.ceramint.2016.04.140.
Habib Gholipour-Ranjbar, Mohammad Reza Ganjali, Parviz Norouzi, Hamid Reza Naderi.
3. Application of Ni/Co-based metal–organic frameworks (MOFs) as an advanced electrode material for supercapacitors, New J. Chem., 2016,40, 9187-9193, https://doi.org/10.1039/C6NJ01449F.
Habib Gholipour-Ranjbar, Mohammad Soleimani, Hamid Reza Naderi.
4. Functionalized graphene aerogel with p -phenylenediamine and its composite with porous MnO2 : investigating the effect of functionalizing agent on supercapacitive performance, Journal of Materials Science: Materials in Electronics, 2016, 27,10163–10172, https://doi.org/10.1007/s10854-016-5093-1.
Habib Gholipour-Ranjbar, Mohammad Reza Ganjali, Parviz Norouzi, Hamid Reza Naderi.
5. Sonochemical synthesis of porous nanowall Co3O4/nitrogen-doped reduced graphene oxide as an efficient electrode material for supercapacitors, Journal of Materials Science: Materials in Electronics, 28, 2017, 14504-14514. https://doi.org/10.1007/s10854-017-7314-7.
Hamid Reza Naderi, Parviz Norouzi, Mohammad Reza Ganjali, Habib Gholipour-Ranjbar.