Redox flow batteries are a reliable option for the storage of energy from renewable resources and the all vanadium cell chemistry features the highest level of commercialization. The storage market demands further cost reductions. A tubular cell design can lower power specific costs by featuring reduced material needs and enabling the use of cost efficient extrusion processes of cell components. The feasibility of tubular all vanadium cells has already been shown in previous studies of the authors. In this study, we report on the progress of a recent cell generation and the integration of single cells into stacks. The performance of the current cell and stack generation has reached the region of planar cells with discharge current densities of i(dch )> 300 mA cm(-2) at SOC approximate to 0.5 and U-cell = 0.8V as well as maximum power densities of P / Area > 300 mW cm(-2) with respect to the membrane area and of P / Volume > 750 kW m(-3) with respect to the cell body volume. The single cell performance turns out to be reproduceable with negligible losses at stack level in a 5p setup. In this way, the feasibility of tubular stacks is demonstrated. We claim the tubular approach to be transferrable to other cell chemistries.

Proton Exchange Membrane Water Electrolyzers (PEMEL) are promising for the production of green hydrogen, but costs have to be reduced and lifetime has to be improved. In this study we investigate PEMEL with low catalyst loading achieved by Atomic Layer Deposition (ALD) and 3D printing of the electrodes. Degradation processes were characterized and allocated using different electrochemical and physicochemical methods. The cell setup was optimized using Distribution of Relaxation Times Analysis (DRT) of the Electrochemical Impedance Spectroscopy (EIS) measurements and the long-term performance of the optimized cell was investigated using different electrolytes (sulfuric acid and deionized water).

Co-extrusion of both half-cells in tubular PEM water electrolyzers can lower the costs for hydrogen production, since the number of components is reduced and the production process is simplified. However, after co-extrusion of the inner half-cell and the ion exchange membrane, the membrane is in its fluoride sulfonyl form and must be hydrolyzed to achieve the proton conductive sulfonic acid to be ready for use. Common practice is the hydrolysis using concentrated alkaline solutions, which causes a corrosion of the laminated anode electrode. We developed a less corrosive method using triethylsilanol as reactant. Tubular membranes hydrolyzed with this new procedure were characterized and tested in an electrolyzer laboratory test setup.

Polymer electrolyte membrane electrolysis (PEMEL) is a technology with a major role in linking the hydrogen production to renewable energy resources with a volatile behaviour such as wind and solar. High amounts of precious metals and a labour intensive production also make it a cost intensive technology. A tubular cell design has the potential to reduce production costs by co-extrusion of cells which feature a reduced sealing length. For the inner half cell, additive manufacturing (AM) of titanium offers a high degree of freedom for the electrode design to reach a high electric conductivity and active surface area. In combination with atomic layer deposition (ALD) of iridium catalyst a porous transport electrode (PTE) can be fabricated. Using planar test cell results and model based PTE design, this study demonstrates the feasibility of a tubular PEMEL cell consisting of an additively manufactured, iridium coated anode PTE in the inner half cell, an extruded membrane and a platinum coated graphite felt cathode PTE in the outer half cell. The outer titanium current collector can be replaced by an extruded graphite polymer compound current collector to reduce the amount of titanium without performance losses. The cell is operated at 60 degrees C in 1 mol L-1 sulphuric acid and experimentally characterized by polarization curves and electrochemical impedance spectroscopy (EIS). At 2.0 V cell potential a current density of approximate to 450mAcm-2 was reached corresponding to an iridium mass specific current density >1500Ag-1 which is significant larger than literature values.(c) 2023 The Author(s). Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. This is an open access article under the CC BY license.

Data presented in the article with the same title

Polymer electrolyte membrane (PEM) water electrolysis is already widely used for hydrogen production but still needs further cost reductions. While tubular cell designs might reduce production costs by extrusion production of cell components and small sealing lengths, catalyst coating methods like atomic layer deposition (ALD) might reduce catalyst costs significantly. This study demonstrates the feasibility of a tubular PEM electrolyzer membrane electrode assembly (MEA) for the oxygen half cell with 5.0 mm diameter. An extruded perfluorosulfonic acid (PFSA) cation exchange membrane is combined with a porous transport electrode (PTE) consisting of a titanium felt with a low iridium catalyst loading obtained by ALD. The performance is experimentally characterized in a complete tubular cell setup by polarization curve and ohmic resistance measurements. Operation in sulphuric acid at a cell voltage of 1.7 V and a cell temperature of 60 degrees C results in an overall current density of 55 mA cm(-1) and an iridium mass activity > 680 A g(-1) which is up to 3 times larger than literature values. The high frequency ohmic resistance of the cell turns out to be 0.96 U cm(-2). Up to the knowledge of the authors, this is the first time, that a tubular PEM electrolysis cell is designed, assembled and characterized. (C) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Activity and durability of a polymer electrolyte membrane (PEM) water electrolysis single cell, assembled with porous transport electrodes (PTEs) with a low catalyst loading were investigated for 500 h. A current density of 160 mA/cm2 and a high mass activity of 1368 A/ gIr were achieved while operating at 60 degrees C with 1 mol/L sulfuric acid. The degradation of the cell was characterized using different electrochemical and physicochemical methods before, during and after operation of the electrolysis cell and a mean degradation rate for the cell of 67 mV/h was determined at 15 mA/cm2. To the best of our knowledge this is the first time that long-term performance of a PEM water electrolysis cell assembled with PTEs coated by ALD is investigated.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

This study establishes the applicability of 3D printing (additive manufacturing) towards the generation of titanium alloy scaffolds for water oxidation electrodes. The scaffolds can be subsequently nanostructured by electrochemical anodization to enhance their surface area and coated with iridium as the electrocatalyst. We focus on the characterization of the functional electrodes in process-relevant conditions (1 M H2SO4, 60 circle C, stirring) in terms of their performance and stability in a holistic manner. Various preparative conditions yield various patterns of performance and stability, as quantified by overpotentials eta 10 in steady-state electrolyses, maximum current densities jmax in dynamic voltammetry, surface roughness rf, and by overpotential increase, iridium loss, and jmax decrease after 100 h of operation, on the other hand. In other words, the system is highly flexible and can be adapted to specific constraints depending on the application chosen.

The limited annual mining capacity and high costs of platinum metal group catalysts (PMG) are confining the production of hydrogen from PEM electrolysis. Therefore, a significant reduction of catalyst needs is crucial to reduce system costs and increase production ca-pacity. This study demonstrates the feasibility of a PEM water electrolysis cell design using porous transport electrodes (PTE) with catalyst coating by atomic layer deposition (ALD) and operation in 1 mol/L sulphuric acid at 60 degrees C. Though the catalyst loading has been reduced to 0.12 mg/cm(2) iridium on the anode and 0.28 mg/cm(2) platinum on the cathode, a current density of 168 mA/cm(2) and mean high mass activity of 1400 A/g iridium could be achieved at 1.7 V. The characterization of three high loading PTE cells is combined with a detailed overpotential analysis from polarization curve fits and demonstrates a repro-ducible cell setup. Further analysis steps show an increasing cell performance with increasing coating cycle numbers and the consistency of the anode performance in the three electrode setup with the complete cell. The ALD coated PTE design turns out to be a promising candidate for catalyst loading reduction in PEM electrolysis. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

We present a vanadium redox flow battery with a tubular cell design which shall lead to a reduction of cell manufacturing costs and the realization of cell stacks with reduced shunt current losses. Charge/discharge cycling and polarization curve measurements are performed to characterize the single test cell performance. A maximum current density of 70 mAcm(-2) and power density of 142 Wl(-1) (per cell volume) is achieved and Ohmic overpotential is identified as the dominant portion of the total cell over potential. Cycling displays Coulomb efficiencies of approximate to 95% and energy efficiencies of approximate to 55%. During 113 h of operation a stable Ohmic cell resistance is observed. (C) 2017 Elsevier B.V. All rights reserved.

Background: Rapid Ventricular Pacing (RVP) is an established technique for temporary arrest of LV ejection during Transcatheter Aortic Valve replacement (TAVI). As microvascular Perfusion (MicrPF) is crucial for adequate tissue oxygenation and potentially linked to outcome, the purpose of this study was to investigate alterations of MicrPF associated with RVP during TAVI. Methods: We studied 29 patients (pts., mean age 81.8±6.9years, n=18 female. Euroscore 33±12%) undergoing RVP during TAVI. MicrPF was analysed using Sidestream-Darkfield (SDF) imaging, which was performed by video recordings of the sublingual microvasculature. SDF-imaging was started 8sec before and continued until 12sec after RVP. The microvascular flow index (MFI), a semi-quantitative scale quantifying the microflow (0: no flow = no flow present for the entire duration of the clip; 1: intermittent flow = flow present <50% of the duration of the clip; 2: sluggish flow = flow present >50% but <100% of the duration of the clip or very slow flow for the entire duration of the clip; and 3: continuous flow = flow present for the entire duration of the clip) was determined repeatedly every 2sec in each video sequence. MFI-calculation was performed by averaging flow in the four quadrants of the video images for small (10-25μm) and medium (26-50μm) sized vessels each by a blinded investigator. Results: After a mean RVP-duration of 14sec (range 6-29), mean arterial pressure (MAP) dropped from 69±14mmHg to 40±7mmHg (p<0.001). This was associated with a significant decrease of mean MFI in small and medium vessels from 2.21±0.65 and 2.35±0.53 to 0.91±0.66 (p<0.001) and 1.09±0.76 (p<0.001), respectively. MFI decreased by 0.108 every two seconds, "no flow" (MFI<1) was oberved in 12pts (41.4%) after a variable RVP-duration. After termination of RVP, MAP rapidly recovered to baseline values (66±12mmHg, p=0.34 vs. baseline). However mean MFI remained significantly below baseline values (small: 1.72±0.81, p=0.001 vs. baseline; medium: 1.86±0.86; p=0.005 vs. baseline) within the next 12 seconds of measurement. Conclusions: RVP during TAVI is associated with a continuous decrease of microflow. Arrest of mircovascular perfusion ("no flow") occurs in a significant proportion of patients and becomes more likely with prolonged RVP. After termination of RVP there is a delayed recovery of microflow despite already normalized MAP.

R E S U L T S V I R E S U L T S V Functional Performance and Structural Maturation of Decellularized Pericardial Valves in Central Venous Position: An Experimental Study Alexander Lauten1, Adrian Laube1, Christoph Willich1, Harald Schubert2, Sabine Bischoff2, Sandor Nietzsche3, Markus Ferrari1, Arthur Lichtenberg4, Hans-R. Figulla1, Payam Akhyari4 1University Heart Center Jena, Department of Cardiology, Jena, Germany; 2Institute of Laboratory Animal Science, Jena, Germany; 3 DElectron Microscopy Center, Friedrich-SchillerUniversity Jena, 4Department of Cardiovascular Surgery and Institute for Experimental Surgery, Duesseldorf University Hospital, Duesseldorf P U R P O S E R E S U L T S I