Formation of desert rose structures in vacuum plasma sprayed electrodes for alkaline electrolysis

The EU FCH-JU RESelyser project is concerned with the development of high pressure, high efficiency and low cost alkaline water electrolysers that can be operated variably and intermittently to meet the demands for integration into energy networks relying on fluctuating renewable energy. The project utilizes NiAlMo alloy electrodes produced at the German Aerospace Center (DLR) by vacuum plasma spraying (VPS). VPS results in a heterogeneous microstructure consisting of a multitude of intermetallic phase sub domains and pores. Prior to electrolysis operation the electrodes are activated by leaching of Al and some Al containing intermetallic phases leaving micrometer pores and nanometer dendritic pores increasing the surface area available for the electrolysis reactions. The vacuum plasma sprayed electrodes were analyzed by high resolution SEM and TEM before and after electrolysis operation and after storage in water. Analyses of cross sections and electrode surfaces revealed desert rose like nano flake structures on the surface and in the pores on several electrodes. The formation of the desert rose structure appeared to be related to the electrolysis operation as well as the duration of storage in distilled water. The size of the faceted flakes varied from tens of nm to a couple of µm where the thickness varied from a few nm to ~50 nm. The desert rose structure was confirmed by TEM to consist primarily of NiO and Al2NiO4 like phases (similar lattice parameters). The possible implications for the application and performance of the electrodes are discussed

Presentación del proyecto QualyGridS: Test estandarizados para la cualificación de electrolizadores desarrollando servicios de red

Starting in January 2017, the QualyGridS (Standardized qualifying tests of electrolysers for grid services) project has as final goal the establishment of standardized testing protocols for alkaline (AE) and Proton Exchange Membrane (PEM) electrolysers running grid services. It is a three years project that receives funding from the European Commission and which starting point is the analysis of the transmission and distribution systems of different regions of Europe presented in this document. While the project goes forward, the most relevant business cases in Europe based on the use of electrolyser will be technically and economically analyzed and the developed test protocols will be experimentally tested on state of the art alkaline and PEM electrolysers up to 300 kW

One step electrochemical fabrication of high performance Ni@Fe-doped Ni(oxy)hydroxide anode for practical alkaline water electrolysis

Oxygen evolution reaction (OER) is a rate-determining process in alkaline water electrolysis (AWE). Herein, we report a novel one-step oxidation-electrodeposition (OSOE) approach to generate core@shell nanoarrays-based AWE electrode with outstanding OER performances: an overpotential of 245 mV at 10 mA cm−2 (Tafel slope: 37 mV dec−1), and excellent stability under huge current densities. Moreover, the alkaline (AEL) cell equipped with NM-OSOE-23 anode recorded significant performance improvement of 200 mV lower voltage (2 A cm−1) compared with a similar cell used bare Ni mesh as an anode, which was contributed by notable enhancements of interface contact, anodic charge transfer, and mass transfer. These promising results are attributed to the constructed specific core@shell Ni@Fe-doped Ni(oxy)hydroxide nanoarray architecture on commercial nickel mesh. This study demonstrates this first reported OSOE can be commercialized to make highly efficient anodes enabling next-generation AWE

Elucidating the performance limitations of alkaline electrolyte membrane electrolysis : dominance of anion concentration in membrane electrode assembly

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.Projekt DEA

Qualifying tests and economic analysis of electrolyzers for grid services

As part of the European project QualyGridS, drafts for standardized testing protocols for electrolyzers to perform electricity grid services are defined and elaborated. These protocols are designed to be used by alkaline and proton exchange membrane (PEM) electrolyzers up to the Megawatt scale. The protocols are being submitted for standardisation. Testing results using these protocols on a state-of-the-art PEM electrolyzer system of 50 kW with 1500 cm2 area stack are presented with considerations of the influence of balance of plant (BOP) components. System behaviour of 50 kW and Megawatt PEM electrolyzers are compared to determine the influence of their scale in performance and response time. An economic analysis has been conducted in the scope of the project. Today’s situation has been analyzed in a first part: the objective was to identify the best way to combine H2 supply for a primary value stream and provision of grid services. A second part of the analysis studied the potential future evolutions that could change the current pictur

Experimental and Numerical Study of the Effect of Gas-Shrouded Plasma Spraying on Cathode Coating of Alkaline Electrolysis Cells

The aim of this work is to improve the performance of electrodes prepared via atmospheric plasma spray by means of gas shrouding which is expected to apparently reduce the oxygen content of the plasma plume and subsequently improve the coating quality. Electrodes with dual-layer coating for alkaline water electrolysis were deposited on Ni-coated perforated substrates. Microstructure and morphology were studied by SEM. Element content was measured by EDS. Enthalpy probe was employed for measuring plasma temperature and velocity as well as the gas composition. For verifying and better understanding the shrouding effect numerical calculation was carried out according to the experimental settings. Electrochemical test was carried out to validate the shrouding effect. The results showed slight protecting effect of gas shrouding on plasma plume and the final coating. Overall the dual-layer region, the measured oxygen fraction was 3.46% and 3.15% for the case without gas shrouding and with gas shrouding respectively. With gas shrouding the coating exhibited similar element contents as the coating sprayed by VPS while no obvious improvement was observed in the microstructure or the morphology. Evident electrochemical improvement was nevertheless achieved that with gas shrouding the electrode exhibited similar performance as that of the VPS sprayed electrode

DMFC as Battery-Extender in solar-boat application

For special applications Direct Methanol Fuel Cells (DMFC) are close to commercial application or already commercialized today. However for the step from laboratory to a broader market of fuel cells, a significant cost reduction, as well as a lifetime and power density improvement of the systems is needed. The Goals of the BZ-BattExt Project should be reached by applying new knowledge in alternative materials, improved operation strategies and enhanced sub systems. In the project a 100 W DMFC compact system as battery extender was successfully developed and operated. The reduction of the number of components and the simplification of the system led to a high reduction in price, weight and volume. The feasibility of a micro-DMFC system was evaluated which enables a minimised system periphery due to an improved System Architecture. For this, alternative materials and functional components were developed and investigated leading to new membranes with reduced water and methanol permeation allowing a low air stoich operation and higher system efficiency. Gas diffusion layers of various compositions were tested and optimised materials were selected. New sealing materials with good methanol stability and optimized processibility in commercial production Processes were developed and the MEA preparation was adapted to the new materials. The use of a simple, cost-effective way of stack production was demonstrated for DMFC use. Using this new components and materials, coupled with the enhanced subsystem architectures and enhanced operation strategies, the build up and start-up of an improved micro DMFC System was achieved. The technical feasibility of the Results was investigated in the real application. The micro DMFC System was used as a battery range extender in a 6m solar boat. The DMFC fuel cell system serves as a basis for an efficient, compact and cost effective alternative for battery- or battery-extender systems and can fulfil a broad variety of applications