Browsing by Author "Gago, Aldo Saul"

Now showing 1 - 4 of 4

Open Access
Advancement of segmented cell technology in low temperature hydrogen technologies
(2020) Biswas, Indro; Sánchez, Daniel G.; Schulze, Mathias; Mitzel, Jens; Kimmel, Benjamin; Gago, Aldo Saul; Gazdzicki, Pawel; Friedrich, K. Andreas
The durability and performance of electrochemical energy converters, such as fuel cells and electrolysers, are not only dependent on the properties and the quality of the used materials. They strongly depend on the operational conditions. Variations in external parameters, such as flow, pressure, temperature and, obviously, load, can lead to significant local changes in current density, even local transients. Segmented cell technology was developed with the purpose to gain insight into the local operational conditions in electrochemical cells during operation. The operando measurement of the local current density and temperature distribution allows effective improvement of operation conditions, mitigation of potentially critical events and assessment of the performance of new materials. The segmented cell, which can replace a regular bipolar plate in the current state of the technology, can be used as a monitoring tool and for targeted developments. This article gives an overview of the development and applications of this technology, such as for water management or fault recognition. Recent advancements towards locally resolved monitoring of humidity and to current distributions in electrolysers are outlined.
Open Access
Elucidating the performance limitations of alkaline electrolyte membrane electrolysis : dominance of anion concentration in membrane electrode assembly
(2020) Razmjooei, Fatemeh; Farooqui, Azharuddin; Reissner, Regine; Gago, Aldo Saul; Ansar, Syed Asif; Friedrich, Kaspar Andreas
Anion exchange membrane water electrolyzers (AEMWEs) offer a cost‐effective technology for producing green hydrogen. Here, an AEMWE with atmospheric plasma spray non‐precious metal electrodes was tested in 0.1 to 1.0 M KOH solution, correlating performance with KOH concentration systematically. The highest cell performance was achieved at 1.0 M KOH (ca. 0.4 A cm-2 at 1.80 V), which was close to a traditional alkaline electrolysis cell with ≈6.0 M KOH. The cell exhibited 0.13 V improvement in the performance in 0.30 M KOH compared with 0.10 M KOH at 0.5 A cm−2. However, this improvement becomes more limited when further increasing the KOH concentration. Electrochemical impedance and numerical simulation results show that the ohmic resistance from the membrane was the most notable limiting factor to operate in low KOH concentration and the most sensitive to the changes in KOH concentration at 0.5 A cm-2. It is suggested that the effect of activation loss is more dominant at lower current densities; however, the ohmic loss is the most limiting factor at higher current densities, which is a current range of interest for industrial applications.
Open Access
Investigation of the degradation phenomena of a proton exchange membrane electrolyzer stack by successive replacement of aged components in single cells
(2025) Kimmel, Benjamin; Morawietz, Tobias; Biswas, Indro; Sata, Noriko; Gazdzicki, Pawel; Gago, Aldo Saul; Friedrich, Kaspar Andreas
Due to their compactness and high flexibility to operate under dynamic conditions, proton exchange membrane water electrolyzers (PEMWEs) are ideal systems for the production of green hydrogen from renewable energy sources. For the widespread implementation of PEMWEs, an understanding of their degradation mechanism is crucial. In this work, we analyze a commercial PEMWE stack via a novel approach of breaking down from the stack to the single-cell level. Therefore, the disassembled stack components are cut to fit into single cells. Then, the aged components are successively replaced with pristine or regenerated components (cleaned and polished), and electrochemical characterizations are conducted to investigate the contributions of the individual components on performance losses. In addition, several underlying degradation phenomena are identified using different physical ex-situ analysis methods. The catalyst-coated membrane (CCM) contributes the most to performance degradation because of contamination and ionomer rearrangement. Additionally, traces of calcium, likely due to insufficient water purification used during operation or for cleaning the cell components, were found. Significant oxidation was observed on the anodic components, while the electronic conductivity on the cathode side remained unchanged. The combination of electrochemical characterization with stepwise regeneration processes and physical ex-situ analysis allows to draw conclusions about the impact of different components on degradation and to analyze the underlying aging mechanisms occurring in each component.
Open Access
Novel pyrrolidinium-functionalized styrene-b-ethylene-b-butylene-b-styrene copolymer based anion exchange membrane with flexible spacers for water electrolysis
(2023) Xu, Ziqi; Delgado, Sofia; Atanasov, Vladimir; Morawietz, Tobias; Gago, Aldo Saul; Friedrich, K. Andreas
Anion exchange membranes (AEM) are core components for alkaline electrochemical energy technologies, such as water electrolysis and fuel cells. They are regarded as promising alternatives for proton exchange membranes (PEM) due to the possibility of using platinum group metal (PGM)-free electrocatalysts. However, their chemical stability and conductivity are still of great concern, which is appearing to be a major challenge for developing AEM-based energy systems. Herein, we highlight an AEM with styrene-b-ethylene-b-butylene-b-styrene copolymer (SEBS) as a backbone and pyrrolidinium or piperidinium functional groups tethered on flexible ethylene oxide spacer side-chains (SEBS-Py2O6). This membrane reached 27.8 mS cm-1 hydroxide ion conductivity at room temperature, which is higher compared to previously obtained piperidinium-functionalized SEBS reaching up to 10.09 mS cm-1. The SEBS-Py206 combined with PGM-free electrodes in an AWE water electrolysis (AEMWE) cell achieves 520 mA cm-2 at 2 V in 0.1 M KOH and 171 mA cm-2 in ultra-pure water (UPW). This high performance indicates that SEBS-Py2O6 membranes are suitable for application in water electrolysis.