For sustainable energy storage, all‐organic batteries based on redox‐active polymers promise to become an alternative to lithium ion batteries. Yet, polymers contribute to the goal of an all‐organic cell as electrodes or as solid electrolytes. Here, we replace the electrolyte with a deep eutectic solvent (DES) composed of sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) and N‐methylacetamide (NMA), while using poly(2,2,6,6‐tetramethylpiperidin‐1‐yl‐oxyl methacrylate) (PTMA) as cathode. The successful combination of a DES with a polymer electrode is reported here for the first time. The electrochemical stability of PTMA electrodes in the DES at the eutectic molar ratio of 1 : 6 is comparable to conventional battery electrolytes. More viscous electrolytes with higher salt concentration can hinder cycling at high rates. Lower salt concentration leads to decreasing capacities and faster decomposition. The eutectic mixture of 1 : 6 is best suited uniting high stability and moderate viscosity.

Silver electrodeposition onto Au(111) has been studied as a function of composition of deep eutectic solvent (DES) type III and IV. The electrochemical investigations were performed by using cyclic voltammetry and in‐situ electrochemical quartz crystal microbalance experiments. Scanning electron microscopy coupled with Auger spectroscopy and atomic force microscopy were used to characterize the deposited metal overlayers. Silver deposition from DES type III shows several analogies to the electrocrystallization from aqueous solutions, such as the presence of underpotential deposition. It is shown that the hydrogen‐bond donor exerts a strong influence on the silver growth mode and on the structure of the metal deposits. In addition, the hydrogen‐bond donor turns out to exert a rather strong influence on the plating process during silver deposition from DES type IV.

Syngas fermentation is a potential player for future emission reduction. The first demonstration and commercial plants have been successfully established. However, due to its novelty, development of syngas fermentation processes is still in its infancy, and the need to systematically unravel and understand further phenomena, such as substrate toxicity as well as gas transfer and uptake rates, still persists. This study describes a new online monitoring device based on the respiration activity monitoring system for cultivation of syngas fermenting microorganisms with gaseous substrates. The new device is designed to online monitor the carbon dioxide transfer rate (CO2TR) and the gross gas transfer rate during cultivation. Online measured data are used for the calculation of the carbon monoxide transfer rate (COTR) and hydrogen transfer rate (H2TR). In cultivation on pure CO and CO + H2, CO was continuously limiting, whereas hydrogen, when present, was sufficiently available. The maximum COTR measured was approximately 5 mmol/L/h for pure CO cultivation, and approximately 6 mmol/L/h for cultivation with additional H2 in the gas supply. Additionally, calculation of the ratio of evolved carbon dioxide to consumed monoxide, similar to the respiratory quotient for aerobic fermentation, allows the prediction of whether acetate or ethanol is predominantly produced. Clostridium ljungdahlii, a model acetogen for syngas fermentation, was cultivated using only CO, and CO in combination with H2. Online monitoring of the mentioned parameters revealed a metabolic shift in fermentation with sole CO, depending on COTR. The device presented herein allows fast process development, because crucial parameters for scale‐up can be measured online in small‐scale gas fermentation.

Invited for this issue's Front Cover is the group of Prof. Timo Jacob in collaboration with Prof. Alexander Kuehne, both from Ulm University (Germany). The cover picture shows copper electrodeposition on a gold‐coated quartz crystal from copper(II) chloride in a choline chloride/ethylene glycol deep eutectic solvent (DES), as monitored by electrochemical quartz crystal microbalance (EQCM). Read the full text of the Research Article at 10.1002/celc.202101263.

Copper electrodeposition on Au(111) from deep eutectic solvents (DESs) type III was investigated employing cyclic voltammetry as well as chronoamperometry. It was further examined on Au(poly) using the electrochemical quartz crystal microbalance (EQCM). The employed DESs are mixtures of choline chloride (ChCl) or choline nitrate (ChNO3) with ethylene glycol (EG) as hydrogen bond donor (HBD), each in a molar ratio of 1 : 2. CuCl, CuCl2, or Cu(NO3)2 ⋅ 3H2O were added as copper sources. Underpotential deposition (UPD) of Cu precedes bulk deposition in chloride as well as nitrate electrolytes. Cu deposition from Cu+ in chloride media is observed as a one‐electron reaction, whereas deposition from Cu2+ occurs in two steps since Cu+ is strongly stabilized by chloride. Cu+ is less stabilized by nitrate and the beginning of bulk deposition in the nitrate‐containing DES with Cu2+ is shifted by several hundred mV to more positive potentials compared to the chloride DES. A diffusion‐controlled, three‐dimensional nucleation and growth mechanism is found by chronoamperometric measurements and analysis based on the model of Scharifker and Mostany.