A modulation QCM applied to copper electrodeposition and stripping

A fast electrochemical quartz crystal microbalance with dissipation monitoring (EQCM−D) was applied to copper electrodeposition and subsequent stripping. Accumulation brings the frequency noise down to the mHz range, corresponding to 0.1 % of a monolayer. With this precision, the apparent mass transfer rate as determined from the time-derivative of the frequency shift can be directly compared to the current. Small but systematic deviations between the two can be attributed to nanoscale roughness. In the voltage range of underpotential deposition (UPD), the apparent mass transfer rate shows peaks and shoulders. The plating additive benzotriazole (BTA) leaves the magnitude of electrogravimetric signals unchanged, but shifts the UPD onset potential. The additive thiourea (TU) promotes UPD and strongly increases the bandwidth

Electrodeposition of Indium from an ionic liquid investigated by in situ electrochemical XPS

The electrochemical behavior and electrodeposition of indium in an electrolyte composed of 0.1 mol/L InCl3 in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py1,4]TFSI) on a gold electrode were investigated. The cyclic voltammogram revealed several reduction and oxidation peaks, indicating a complex electrochemical behavior. In the cathodic regime, with the formation of an In-Au alloy, the reduction of In(III) to In(I) and of In(I) to In(0) takes place. In situ electrochemical X-ray photoelectron spectroscopy (XPS) was employed to investigate the reduction process by monitoring the oxidation states of the components during the cathodic polarization of 0.1 mol/L InCl3/[Py1,4]TFSI on a gold working electrode under ultra-high vacuum (UHV) conditions. The core electron binding energies of the IL components (C 1s, O 1s, F 1s, N 1s, and S 2p) shift almost linearly to more negative values as a function of the applied cell voltage. At −2.0 V versus Pt-quasi reference, In(I) was identified as the intermediate species during the reduction process. In the anodic regime, a strong increase in the pressure in the XPS chamber was recorded at a cell voltage of more than −0.5 V versus Pt quasi reference, which indicated, in addition to the oxidation reactions of In species, that the oxidation of Cl− occurs. Ex situ XPS and XRD results revealed the formation of metallic In and of an In-Au alloy

Biodegradable Zn-ion battery with a lignin composite electrode and bio-ionic liquid based electrolyte: Possible: In situ energy generation by lignin electrocatalysis

Copyright © 2021 The Author(s). Electrochemical energy storage with lignin-based composite electrodes offers a cheap and renewable source for batteries. Lignin composites have mainly been used in supercapacitors and little has been investigated related to applying these composites in batteries. Here we show a biodegradable hybrid Zn-ion battery with a polymer/lignin composite electrode as a cathode, a Zn anode and bio-ionic liquid electrolytes. Interestingly, the polymer/lignin composite cathode led to a higher discharge capacity compared to the charge capacity over the entire 100 charge/discharge cycling process. It was observed that the lignin concentration in the composite polymer electrode was crucial in obtaining such a phenomenon. Using SEM, electrochemical analysis and NMR, we showed that lignin electrocatalytically oxidizes during battery charging, which produced the extra energy. This results in obtaining a higher discharge capacity compared to the charge capacity. It is anticipated that such an electrocatalytic technique can be extended to other battery systems to harness clean electrochemical energy from biomass.BMBF project ZIB 03XP0204

Study of PLA pre-treatment, enzymatic and model-compost degradation, and valorization of degradation products to bacterial nanocellulose

It is well acknowledged that microplastics are a major environmental problem and that the use of plastics, both petro- and bio- based, should be reduced. Nevertheless, it is also a necessity to reduce the amount of the already spread plastics. These cannot be easily degraded in the nature and accumulate in the food supply chain with major danger for animals and human life. It has been shown in the literature that advanced oxidation processes (AOPs) modify the surface of polylactic acid (PLA) materials in a way that bacteria more efficiently dock on their surface and eventually degrade them. In the present work we investigated the influence of different AOPs (ultrasounds, ultraviolet irradiation, and their combination) on the biodegradability of PLA films treated for different times between 1 and 6 h. The pre-treated samples have been degraded using a home model compost as well as a cocktail of commercial enzymes at mesophilic temperatures (37 °C and 42 °C, respectively). Degradation degree has been measured and degradation products have been identified. Excellent degradation of PLA films has been achieved with enzyme cocktail containing commercial alkaline proteases and lipases of up to 90% weight loss. For the first time, we also report valorization of PLA into bacterial nanocellulose after enzymatic hydrolysis of the samples

The ionic liquid–vacuum outer atomic surface: a low-energy ion scattering study

We have identified elements present in the ionic liquid–vacuum outer atomic surface of 23 ionic liquids using high sensitivity low-energy ion scattering (LEIS), a very surface sensitive technique. We show that the probability of cationic heteroatoms being present at the ionic liquid–vacuum outer atomic surface is very low; we detected imidazolium nitrogen for only one of the 18 imidazolium based ionic liquids investigated, no nitrogen for the two ammonium based ionic liquids and a very small amount of phosphorus for two of the three phosphonium-based ionic liquids. We determine that the anion is always present at the ionic liquid–vacuum outer atomic surface, even for very large cations containing dodecyl alkyl chains or longer; these chains dominate the ionic liquid–vacuum outer atomic surface, but are not sufficiently densely packed to completely cover the anions. We demonstrate the presence of strong hydrogen bond acceptor adsorption sites at the ionic liquid–vacuum outer atomic surface. We demonstrate that the amount of ion present at the ionic liquid–vacuum outer atomic surface can be tuned by varying the size of the other ion; larger cations (or anions) occupy more of the ionic liquid–vacuum outer atomic surface, leaving less room for anions (or cations). By identifying elements present at the ionic liquid–vacuum outer atomic surface, conclusions can be drawn on the orientations of anions nearest the vacuum. We show that for five different anions there is a most probable ion orientation, but other anion orientations also exist, demonstrating the presence of multiple anion orientations. The imidazolium cations nearest to the vacuum also show similar multi-orientation behaviour. This variety of atoms present and therefore ion orientations is expected to be central to controlling surface reactivity. In addition, our results can be used to quantitatively validate simulations of the ionic liquid–vacuum surface at a molecular level. Overall, our studies, in combination with literature data from different techniques and simulations, provide a clear picture of ionic liquid–vacuum outer atomic surfaces