Next Generation PEM Electrolysers under New Extremes ...




 D1.1 - Project Shared Workspace Implemented and Operiational - CONFIDENTIAL

To fulfil two fundamental internal project communication requirements: i) efficient exchange between partners of information about NEPTUNE project ii) decentralised and secured archiving of the documents generated, one independent and secured web-based communication tool: Project Shared Workplace – PSW has been implemented with a restricted access for project partners only. Among all the functionalities installed on this PSW, for now partners have a total access to the following tools:
- Document sharing and archiving
- Meeting organization
- General project communication
- Online working document
The PSW maintenance is therefore an on-going activity that will go along with the project lifetime


D2.1 - Harmonised test protocols for assessing system components, stack and balance of plant in a wide range of operating temperature and pressures - PDF

The objectives of this deliverable are to define characterisation and testing protocols for the assessment of performance, efficiency and durability of PEM electrolyser components, stack and balance-of-plant developed in the project to address wide operating conditions in terms of operating current density, temperature and pressure.
The procedures and methods defined within are a set of protocols for ex-situ and in-situ characterisation of active components such as membranes, catalysts, and electrode-membrane assemblies (MEAs). Included are steady-state and accelerated durability tests as well as performance evaluation under specific operating conditions.
These test protocols are also addressed to the assessment of performance, efficiency and durability of a PEM water electrolyser (PEMWE) stack operating under high current density (up to 8 A cm-2), high temperature (up to 140 °C) and high pressure (up to 100 bar). For operation under such extreme conditions, the stack has to be surrounded by a specifically designed balance of plant. Accordingly, specific procedures are regarding an evaluation of the overall PEM electrolysis system under the operating conditions targeted within the project.
The procedures essentially include polarization curves, differential pressure operation, gas crossover analysis and durability tests. A protocol for stack failure analysis is formulated and the aspects related to safety issues are also discussed. For what concerns the balance of plant, particular efforts are addressed to assess the dynamic behaviour of such advanced electrolyser. Specific protocols regard load and on-off cycles, assessment of the dynamic performance using specific current profiles simulating intermittent operation.
In parallel, the aim of this activity is also to implement the harmonised characterisation protocols developed by the Joint Research Laboratory of the European Commission (JRC-IET) for testing MEAs & stacks with an extension of operating conditions to address the specific NEPTUNE project targets. The definition of these protocols will serve as an input for both the harmonization efforts within the FCH JU program but also to provide input to subsequent specification work as well as to enable planning of the test activities in WP3, WP4, WP5 and WP6.
The specific procedures are thus addressed to:
- Mapping of system level requirements to component level requirements
-Define a set of protocols for assessing the PEM electrolysis system under stationary conditions in terms of performance, efficiency & durability.
- Define a set of procedures for the assessment of PEM electrolyser system in relation to the operation under specific duty cycles.


D.3.1 – Supply of 1st Generation Reinforced, Recast and Extruded Aquivion® Membrane and Ionomer Dispersions for High Temperature and High Pressure Operation - PDF

Deliverable D3.1 is aimed at the definition of the first generation of Aquivion-based membrane and ionomer for electrolysis operation under Neptune conditions. In this regard extruded E98-05S membrane (prepared using newly introduced quality inspection system), recast and reinforced membranes were prepared and characterized. Reinforced membranes were produced using novel Torlon PAI support produced via forcespinning after selection of the most promising commercial grade for this application. The three different membrane grades were evaluated in terms of proton conductivity by varying RH, mechanical properties, water uptake and dimensional stability upon soaking in hot water. Although promising, Torlon-based Aquivion-reinforced membranes are considered as not mature enough to be used in the Neptune final stack and the downselection was restricted to recast and extruded membranes.


D.3.2 – Provision of Selected Aquivion® Membrane and Ionomers for large-area MEA Manufacturing (TRL5) - CONFIDENTIAL

Deliverable D3.2 is divided in three parts. In the first part the selection criteria defined to evaluate produced membranes (deeply described in Deliverable D3.1) are presented and discussed. Selection criteria take into account different parameters such as performance (electrochemical, mechanical and gas transport properties), expected membrane quality of the final large-area roll and technology maturity in terms of technology readiness level (TRL). In the second part, Aquivion-based membranes prepared through melt extrusion, dispersion casting and impregnation of ePTFE and Torlon supports are ranked in accordance with the selection criteria described in the first part whereas the membrane roll (namely Aquivion E98-05S) provided for MEA fabrication for the final Neptune stack is described in the third part.


D.3.3 – Report of Scaling-up and Industrialization of Down-selected Aquivion® PFSA Membranes and Ionomer Dispersions - CONFIDENTIAL

Deliverable D3.3 describes the industrial processes aimed at producing Aquivion E98-05S and D98-06AS, respectively the membrane and polymer dispersion selected to be used as raw material to fabricate Membrane Electrode Assembly (MEA) for the Neptune final stack. This deliverable also presents the improvements/process optimizations implemented in both lines. Quality control of extruded membranes was improved introducing a high-speed optical inspection system aimed at identifying and quantifying defects of membranes. Stabilization step, key for materials targeted to electrolysis applications, was optimized by tuning the operating conditions. Process efficiency was assessed through evaluation of fluoride emission rate using Fenton’s test.


D.3.4 – Public Report on Membrane Development for Electrolysis Applications

Deliverable D3.4 is a public extract of Deliverable D3.2 “Provision of selected Aquivion® membrane and ionomers for large-area MEA manufacturing (TRL5)” and D3.3 “Report of scaling-up and industrialization of down-selected Aquivion® PFSA membranes and ionomer dispersions”. The aim of this deliverable is to present the criteria taken into consideration for the selection of the most suitable Aquivion-based membrane to be used for the Neptune final stack, to rank the four grades prepared, to describe the production of the selected materials and process improvements implemented.


D4.1 – Data-set on catalytic activity, electrochemical performance and stability of enhanced catalysts - PDF

The purpose of this Deliverable was to develop enhanced PEM electrolysis components characterised by a significant decrease of the noble metal content and an increase of the current density with respect to the state-of-the art. Membrane-electrode assemblies (MEAs) based on a novel Aquivion® membrane, specifically designed for water electrolysis, with enhanced Ir0.7Ru0.3Ox, Pt/C and Pt-Alloy catalysts have thus been developed and assessed in this work in terms of performance and durability using low catalyst loadings. In this deliverable, we are operating the MEAs at an electrolysis current density (4 A·cm-2) in accordance with the project targets in the presence of a significant reduction of the total noble metal loading (0.44 mg·cm-2 MEA) while maintaining a very high conversion efficiency (>80%).
The specific activity are thus addressed to:

  • The development of oxygen evolution electro-catalysts. The main approach of this task regards the improvement of the intrinsic activity and stability through tailoring anode catalyst surface chemistry, electronic effects and crystallographic orientation. The aim is to produce stable nanostructured solid solutions of Ir and Ru with a core-shell configuration consisting of Ir enrichment on the surface and optimised crystallographic orientation.
  • The development of hydrogen evolution electro-catalysts. As for the anode catalyst, noble metal-based cathode catalysts are necessary to provide corrosion resistance in acidic environment and appropriate catalytic activity for hydrogen evolution. These are essentially based on Pt. The aim of this task is to further reduce the cathode catalyst loading to less than 0.1-0.05 mg cm-2, increase current density up to 4-8 A cm-2 while keeping the low overpotential characteristics of the hydrogen evolution process. Pt electrocatalysts for cathodic operation will be supported on a stable carbon nanofibres support to substitute microporous carbon blacks.
  • The development of anode integrated recombination catalyst. This task is addressing the development of an unsupported recombination catalyst based on a Pt-alloy with core-shell structure. A thin layer recombination catalyst, with ultralow PGM loading, will be integrated in the anode structure at the interface with the membrane to electrochemically oxidize permeated hydrogen that has not recombined inside the membrane. The aim is to limit the hydrogen content in the oxygen stream below a limit of 0.2-0.5% at high differential pressures (100 bar) through a dual layer recombination process.

D4.2 – Manufacturing of catalysts meeting the specifications and provision for large area MEAs and stack - CONFIDENTIAL

Main scientific and technical achievements for catalyst development in WP4 were concerning with the development of designed anode, cathode and recombination electro-catalysts capable of achieving the targeted electro-catalytic activity under specific operating conditions according to the project milestones. Other relevant aspects were the reduction of the noble metal loading versus baseline formulations, the development of cost-effective formulations based on Pt/C catalyst for the cathode and Ir-Ru oxide and Pt-Co (RC) catalysts for the anode with high performance characteristics. Excellent catalytic activity for a recombination catalyst has been demonstrated. Carbon black supported nanosized Pt (CNR-ITAE) and IrRu-oxide electrocatalysts (CNR-ITAE) with enhanced mass activity have been developed for hydrogen and oxygen evolution reactions (HER and OER), respectively, in PEM electrolysers. The investigation of anode and cathode overpotentials at 90°C indicated an overall overpotential of 209 mV vs. the onset potential for water splitting. This was resulting from 160 mV overpotential for the oxygen evolution and 49 mV overpotential for hydrogen evolution processes, respectively. The recombination catalyst allowed to decrease the H2 concentration in the oxygen stream to less than 0.2 % at 55°C and 4 A cm-2 whereas the voltage degradation in a test of more than 2000 h at 4 A cm-2 was less than 5 μV h-1 (in the last 1000 h). All these results are in line with MS3 and MS7 milestones. The developed electrocatalysts were assessed in terms of performance and stability in single cell and down-selected for use in the stack. Scaling up of the down-selected formulations has been addressed with the production of anode, cathode and recombination catalysts in sufficient amount for MEA and stack development and assessment activities (MS4). The selected electro-catalysts have been provided to WP5 for large area MEAs manufacturing.


D4.3 – Public report on catalyst development for electrolysis applications

This deliverable is mainly addressed to the development and characterization of high performance nanostructured Ir0.7Ru0.3Ox, Pt/C and Pt-alloy electro-catalysts achieving a current density of 4 A cm-2 at about 1.85 V (>80% enthalpy efficiency) with a low catalyst loading (0.64 mg cm-2). The specific activity are thus addressed:

  • To investigate various Pt-based materials (unsupported Pt, PtRu, PtCo) as catalysts for recombining hydrogen and oxygen back into water. The recombination performance correlated well with the surface Pt metallic state. Alloying cobalt to platinum was observed to produce an electron transfer favouring the occurrence of a large fraction of the Pt metallic state on the catalyst surface. Unsupported PtCo showed both excellent recombination performance and dynamic behaviour. In a packed bed catalytic reactor, when hydrogen was fed at 4% vol. in the oxygen stream (flammability limit), 99.5% of the total H2 content was immediately converted to water in the presence of PtCo thus avoiding safety issues. The PtCo catalyst was thus integrated in the anode of the membrane-electrode assembly of a polymer electrolyte membrane electrolysis cell. This catalyst showed good capability to reduce the concentration of hydrogen in the oxygen stream under differential pressure operation (1-20 bar), in the presence of a thin (90 um) Aquivion membrane. The modified system showed lower hydrogen concentration in the oxygen flow than electrolysis cells based on state-of-the-art thick polymer electrolyte membranes and allowed to expand the minimum current density load down to 0.15 A cm-2. This was mainly due to the electrochemical oxidation of permeated H2 to protons that were transported back to the cathode. The electrolysis cell equipped with a dual layer PtCo/IrRuOx oxidation catalyst achieved a high operating current density (3A cm-2) as requested to decrease the system capital costs, under high efficiency conditions (about 77% efficiency at 55°C and 20 bar). Moreover, the electrolysis system showed reduced probability to reach the flammability limit under both high differential pressure (20 bar) and partial load operation (5%), as needed to properly address grid-balancing service.
  • To investigate membrane-electrode assemblies based on chemically stabilised short-side-chain proton exchange Aquivion® membranes, prepared by extrusion or recast methods, for operation at high current density (3-4 A cm-2) in water electrolysis cells. A thickness of 90 μm was selected for these perfluorosulfonic acid membranes in order to provide proper resilience to hydrogen crossover under differential pressure operation while allowing operation at high currents. The membranes showed proper mechanical strength for high-pressure operation and suitable conductivity to reduce ohmic losses at high current densities. Both membranes showed excellent performance in electrolysis cells by achieving a voltage efficiency better than 85% and 80% (1.85 V) at 3 and 4 A cm-2, respectively, in polarisation curves at 90 °C. A smaller surface roughness was observed from atomic force microscopy for the recast membrane compared to the extruded one. This may affect the intimate contact between the ionic clusters of the membrane and the catalyst agglomerate at the interface producing a catalytic enhancement in the activation region of the polarisation curves in the case of the recast membrane. At high cell voltages, the polarisation resistance was instead slightly lower for the cell based on the extruded membrane. Interestingly, the different characteristics of the membrane-electrodes interface produced lower recoverable losses in durability studies for the recast membrane-based electrolyser allowing stable operation at both 3 and 4 A cm-2. Hydrogen crossover analysis at a differential pressure of 20 bar showed low gas permeation through both membranes allowing for a wide load range (15-100 %) and high faradaic efficiency >99% at practical current densities (1-4 A cm-2).

D5.1 - Assessment of membrane electrode assemblies for high temperature and high-pressure operation - PDF

The NEPTUNE project develops a set of breakthrough solutions at materials, stack and system level to operate at high temperature (90-140ºC) and high nominal current density (4 A⋅cm-2), while keeping the energy consumption <50 kWh/kg H2 and directly produce hydrogen at 100 bars. The relative high stack temperature is managed by using an Aquivion® membrane. The aimed high efficiency at elevated current density is realised using a 50 μm thin reinforced Aquivion® membrane, able to withstand high differential pressures. The gas crossover is safely managed by adding an efficient recombination catalyst. Improved electrocatalysts with high activity and stability has been developed. The developed improved precursors have allowed the manufacture of well performing MEAs with ultralow catalyst loadings (0.44 mgPGM/cm2). MEAs added 0.2 mg recombination catalyst per cm2 fulfils the ambiguous NEPTUNE performance targets of <1.75 V at base load (4 A/cm2) and <2.2 V at peak load (8 A/cm2). Furthermore, degradation rates ≈ 5 μV/h are measured for these ultralow PGM loaded MEAs.


D5.3 - Public report on MEA development and characterization - PDF

The activities reported in this deliverable regard MEA development studies carried out in the FCH JU Neptune project. Specific efforts were addressed to optimising catalyst ink composition and improving the procedure of ultrasonic catalyst coating on membranes for ultra-low catalyst loadings (IRD). The catalyst ink optimisation activity was addressed to tailor catalyst-ionomer composites as a function of ionomer equivalent weight and catalyst morphology to extend the reaction interface and favour a high degree of catalyst utilisation (CNR). These were pre-requisite to achieve MEA performance of 4 A cm-2 at 1.75 V using an ultra-low PGM loading < 0.4 mg cm-2 MEA (project target). The improvements were also addressed to minimise waste and improve stability. An iterative approach included optimisation of amount of solvent, additives and processing parameters used. MEA characterisation was used to screen the different formulations and preparation procedures and served to assess the achievement of the project targets (CNR). Electrochemical and physico-chemical characterisation addressed to provide insights into the optimal electrode structure (CNR). The aim was to maximize electrochemically active surface area, minimize losses due to transport of charge carriers as well as reactants and products. Electrochemical testing included: - Single cell testing in a wide range of temperatures (from ambient to 140 °C) and pressures (from ambient to 20 bar) as well as in a wide range of current densities (up to 8 A cm-2) - Determination of gas permeation using high sensitivity gas sensors and gas chromatographic analysis to evaluate the capability of the recombination catalysts inside the MEAs to manage gas permeation at high pressure.


D7.1 - Design of a project identity and project templates (presentations, logo) - PDF

The communication of the project will be unified along a common visual entity. A coherent visual chart (colours, fonts, designs) will be derived from the project logo and provided in several shapes and formats (document templates etc.). This visual identity will be used extensively throughout the project, creating a distinguishable brand that will be recognized by the various communities.


D7.2 - Project website and database for dissemination - PDF

The NEPTUNE project website is designed to fulfil project communication and dissemination needs for the benefit of the whole scientific community and the public through relevant information including:

  • project overall objectives, partner & work packages information
  • project activities: news, meetings
  • project progress: technical publications, conference presentations, public domain reports
  • project resources: links, related events …
  • project contact information

All the partners will collectively participate in the dissemination objective of the website by providing up-to-date information The contact database has been implemented to provide a powerful - dissemination and networking tool, it will be updated on a regular basis.


D7.3 - Dissemination and knowledge management protocol - CONFIDENTIAL

This report presents the dissemination protocol for the NEPTUNE project, the procedure for “Open Access” to peer reviewed research articles, internal rules, information on support from the EU members and the strategy for Knowledge Management within the project.

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