Aus dem Labor

Electrochemical energy plays a key role in bringing sustainable form of energy into our daily life thereby replacing traditional and non-renewable energy forms. Naturally, electrochemistry and electrochemical cells becomes a topic of relevance for students.

In our research group, we aim to teach our students how to build a lab-scale polymer-electrolyte membrane (PEM) fuel cell as a part of the curriculum to help and understand its principle. In this cell, platinum doped carbon particles are evenly coated over carbon paper as cathode and anode material.

Simultaneously, Nafion membrane is activated and is later sandwiched between the electrodes to produce a PEM cell. Silver wires are fixed to either sides of the electrodes. 3-D printing is used to produce the outer chambers of the cell into which the PEM cell is sealed. Hydrogen and oxygen are then supplied through the nozzles of the cell chamber to activate the proton-exchange process. Voltage and conductivity studies are then carried out for analysis of the cell.

Gayathri Janarthanam

In the modern world there is a desire to transition towards clean and sustainable energy to protect the planet and reverse the effects of climate change. However, there is a periodically altering daily and seasonal difference in human energy demand and natural renewable energy supply. To match them excess energy has to be withdrawn and saved for later uses. Thus, obviously energy storage technologies have to be applied.

One promising energy storage technology is redox flow batteries (RFB), a type of an electrochemical energy storage device that converts chemical energy into electrical energy through reversible oxidation and reduction of working fluids. The concept was initially conceived back in 1970.

The general structure of RFBs consists of positive and negative electrolyte reservoirs, an electrode-membrane assembly (called the stack) and pumps for flowing the electrolytes over the electrodes. These electrolytes flow over the stack where reversible oxidation and reduction reactions take place. The two half cells are typically separated using an ion-selective semi-permeable membrane. A conversion between the oxidized and reduced form of the redox couple leads to charging/discharging of the battery.

The aim of the actual investigation is to study the kinetics of an electron transfer at platinum electrode in a deep eutectic solvent for the Cu(I)/Cu(II) and Fe(II)/Fe(III) redox couples, that may be considered as the initial step towards engineering of an effective RFB based on these electrochemical processes. Cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS) predominantly were used as the means for kinetics study.

Arkadz Bureika

There is an increased interest in the development for more clean, sustainable, and eco-friendly materials in order to prevent environmental pollution as much as possible. Since cellulose is the earth's most abundant polymer, it is a low-cost material that almost everywhere available or at least cultivable. Different nanoscale materials can be obtained from it such as cellulose nanocrystals, cellulose nanofibers, and bacterial nanocellulose. These nanoparticles present different characteristics and different approaches are used to extract each of them. Cellulose nanomaterials present low production cost, low density, and are a sustainable alternative to many petroleum-based materials. Therefore, the objective of the project was to obtain cellulose nanocrystals from wastepaper by using an acid hydrolysis method.

Carolina Gregorio Costa

Chalcopyrite materials and in particular ternary chalcogenides like the semiconductor materials CuInS₂ and CuGaS₂ have drawn significant attention as promising compounds in optoelectronic devices, e.g. solar cells or photocatalysts. In those applications the electronic structure of the semiconductor, that determines the band gap and band edges, is of great importance and can be influenced in various ways. For example, by alloying it with matching materials or by introducing defects in the structure that form due to nonstoichiometric compositions. In this project work the tuning of the band gap through the above-mentioned measures was investigated via quantum chemical density functional theory (DFT) calculations that allowed the simulation of the band structure for pristine, alloyed and disordered CuInS₂ and CuGaS_2.

Atoosa Gonabadi