Ralf Peipmann

Novel amperometric sensors for nitrite detection using electrodes modified with PEDOT prepared in ionic liquids

AbstractNovel amperometric sensors based on poly-3,4-ethylenedioxythiophene (PEDOT) were prepared and characterized for nitrite detection. An experimental matrix of two substrate materials (glassy carbon and gold) and four electrolytes used for preparation of electrodes (water, acetonitrile, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide) were investigated for the preparation of the sensors. The obtained films were characterized using scanning electron microscopy, cyclic voltammetry, amperometry, and electrochemical quartz crystal microbalance. Both glassy carbon and gold electrodes modified with PEDOT showed excellent electrocatalytic activity toward nitrite oxidation. An improved influence of the electrodes prepared in ionic liquids could be observed for the detection of nitrite, expressed by higher electrocatalytic activity and better sensitivities. The sensors showed good stability, while only weak interferences with selected cations, anions, and small biomolecules were detected. Graphical Abstractᅟ

Understanding the charge storage mechanism of conductive polymers as hybrid battery-capacitor materials in ionic liquids by in situ atomic force microscopy and electrochemical quartz crystal microbalance studies

Safe and sustainable energy storage systems with the ability to perform efficiently during large numbers of charge/discharge cycles with minimum degradation define the main objective of near future energy storage technologies. Closing the gap between high power and energy per unit weight requires new materials that can act as a battery and capacitor at the same time. Conductive polymers have attracted attention as hybrid battery-capacitor materials. However, their potential impact has not been fully investigated because their behaviour, especially in non-aqueous electrolytes such as ionic liquids, is not completely understood. Here, we aim to clarify the fundamental functionality of these hybrid characteristics while studying the interaction between a conductive polymer and an ionic liquid by in situ atomic force microscopy and electrochemical quartz crystal microbalance. The main achievement is the visualisation of the morphological modifications of the conductive polymer depending on the state of charge. These modifications significantly influence the viscoelastic material properties of the polymer. Our combined findings provide a model which explains why conductive polymers behave like (pseudo)-capacitors at a high state of charge and as batteries at a low state of charge. This understanding enables application-orientated synthesis of conductive polymers and their use as high-performance energy storage materials.

Electrodeposition of Cuprous Oxide on Boron Doped Diamond Electrodes

Nowadays, Cu_2O is very promising electrode material for photoelectrochemical applications. In this paper, we report on the controllable synthesis of Cu_2O single particles as well as compact layers on Boron Doped Diamond (BDD) electrodes using potentiostatic deposition in continuous and pulse mode. The BDD layers were prepared with different B/C ratios in the gas phase in order to investigate boron doping level influence on the Cu_2O properties. The effect of electrodeposition conditions such as deposition regime and pulse duration was investigated as well. The Cu_2O covered BDD electrodes were analysed by Scanning Electron Microscopy (SEM) and Raman spectroscopy. Improvement in the homogeneity of the electrodeposit and removal of clusters were achieved when the pulse potentiostatic regime was used. Using the same pulse electrodeposition parameters, we confirmed the possibility of controlling the deposition rate of Cu_2O by varying the BDD conductivity. Finally, we were able to scale the size of Cu_2O particles by changing the number of deposition pulses. The obtained results have shown a great potential of controlling the morphology, amount, size and distribution of Cu_2O films on BDD substrates by changing the boron doping level and electrodeposition conditions as well. The investigations reported herein allowed us to better understand the deposition mechanism of Cu_2O on BDD electrodes which could then be used for preparation of active layers for electrochemical applications and in optoelectronic devices such as solar cells and photodetectors.

Vanadium redox flow batteries diagnostics adapted for telecommunication application

One of the main factors limiting the development of modern telecommunication devices and systems is finding reliable and efficient energy storage technologies. The Vanadium Redox Flow Battery (VRB) is an emerging candidate that has a high potential to be deployed for such an application. However, the VRB needs a robust control and monitoring system to predict their state of health and to foresee any failures. In this work, we present a nondestructive testing procedure for a VRB. The proposed testing procedure is based on the analysis of equivalent electrical circuit parameters identified by impedance or transient characteristics. Since the suggested approach requires only a small volume of data for transmission, it allows organizing the diagnostic system of energy storages for stationary telecommunication objects.

A STM Investigation on Step Dynamics during Cu Electrodeposition. Part I - Development of the Electrolyte.

The present work deals with the electrochemical deposition of copper on Pt(1 1 1) substrates and in particular with the evolution of the surface morphology. To monitor this evolution, scanning tunneling microscopy (STM) was used. It is well known that organic molecules can act as levelers or brighteners in industrial electrochemical deposition processes. To get an insight in their interaction with metal growth cytochrome c was chosen to mimic these organics. Cytochrome c was singled out because it is a large metalloproteine, thus being easy to identify by STM. Other suitable candidates for the interference with crystal growth can be nano particles. Metallic nano particles, e.g. made of Au or Pt, are inherently conductive and, thus, easily recognized by STM. Their organic shell (stabilizing their size) can be used to attach them to the substrate surface. The STM results obtained were compared to a theoretical model.