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Cost-effective PROton Exchange MEmbrane WaTer Electrolyser for Efficient and Sustainable Power-to-H2 Technology

Periodic Reporting for period 2 - PROMET-H2 (Cost-effective PROton Exchange MEmbrane WaTer Electrolyser for Efficient and Sustainable Power-to-H2 Technology)

Reporting period: 2021-10-01 to 2023-03-31

The need for de-carbonization of our society is a pressing issue raising the attention at social and political levels. The production of high value chemicals and fuels such as methanol requires hydrogen derived at the moment from hydrocarbons and resulting in large emissions of CO2. Green Hydrogen produced by water electrolysis coupled to renewable sources could be the ultimate solution to this problem. Proton exchange membrane water electrolysis (PEMWE) is the most suitable technology for this process due to its compactness and flexibility. However, the dependence on precious metal catalysts and expensive components manufactured in titanium poses a serious threat for the scale up and market penetration of this technology. PROMET-H2 project aims to develop a pressurized PEMWE with the lowest capital cost ever achieved. The main objective of PROMET-H2 project is to decrease the capital cost of the PEMWE from 1000-1500 €/kW to 500-700 €/kW without compromising its performance and durability, and replacing noble metals with others that are more benign from an environmental and economic point of view. The materials and components that will make this possible have already been demonstrated in laboratory and in PROMET-H2 these innovations will be implemented in a 25 kW PEMWE system. Such electrolyser will be coupled with a methanol production pilot plant from CO2. Many recycling processes for Platinum Group Metals (PGMs) and other valuable materials recovery from End of Life (EoL) PEM systems have been addressed. Most of them suffer from low recovery yields, high operational cost and negative environmental impact. PROMET-H2 will develop a fast, versatile and environmentally friendly hydrometallurgical leaching process for recycling of Critical Raw Materials (CRMs) from membrane electrode assemblies (MEAs) in high recovery yields.
Highly efficient and durable membrane electrode assemblies have been developed by integrating novel electrocatalysts with low CRM materials and will impact the next generation of components for PEM electrolysers. The tested CRM-free electrodes showed promising performances but unfortunately far away from the CRM-based catalysts. Thus, in the second period, PROMET-H2 has decided focus on the CRM drastic reduction route. Two promising candidates were selected for the OER: Iridium deposited on antimony tin oxide (ATO) (CENMAT) and the Ir mixed oxide (CSIC). DLR developed an MEA with 0.2 mgIr cm-2 using Ir mixed oxides (Sr2CaIrO6 perovskite). With a cell voltage of 1.81 V at nominal current density of 2 A cm-2, the performance full fill PROMET-H2 targets with a successful 1000 h long-term test at constant 2 A cm-2 demonstrated the Ir content in the MEA can be drastically reduced without compromising performance or durability. In parallel FZJ measured similar performances with 0.2 mgIr cm-2 using Ir ATO (CENMAT). The activation at MEA level and scalability potential were the arguments for PROMET-H2 to selected the Ir ATO to produce the MEAs for the NEL and PROPULS short stacks. The MEAs produced by FZJ have been already sent to Propuls and NEL. Chemours continued with the development of novel membranes (80 µm thickness) that showed remarkably lowered H2 cross-over (ca. 0.2% H2 in O2) and was able to fulfill PROMET-H2 target of < 2% H2 in O2 at 0.5 A cm-2. But some stability studies and internal Chemours decision excluded the membrane for assembly in the PROMET-H2 stacks. MONOLITHOS develops a low cost and simple recycling process that allows the reuse of the catalysts, which is necessary for environmental and economic reasons. The hydrometallurgical leaching process for PGMs recovery developed by MONOLITHOS is proposed for CRMs recovery from End-of-Life PEMWE MEAs with efficiency higher than 99% for Pt content and 60% for Ir. Stainless steel (SS) based bipolar plates (BPP) were coated and tested with dense coatings (Nb/Ti) by vacuum plasma spray. Electrochemical accelerated stress tests in acid environment verified the stability of the coatings protecting the stainless steel from corrosion. These BPPs have lower cost than the state-of-the-art Ti-based ones. In order to study the restricted performances at stack level using low Ir loadings (0.2mgIrcm-2) PROMET-H2 will compare 3 different PTLs coatings: two with PGM low content and one without PGM. The 3 different configurations of PTLs were sent to NEL. The short stack with PROMET-H2 MEAs was assembled at NEL and has been purchased to FZJ and it will be tested in the last period of the project. From results obtained in the second period, PROMET-H2 will try use SS-BPP without any coating in the PROMET-H2 stack. The baseline stack is ready to be tested in the last period of the project. DLR has develop a segmented cell for the Propuls novel Hydraulic stack. The segmented cell has been designed with 44 segments (approx. 4.8 cm2 segment area) and 16 temperature sensors giving the chance to measure independently the current in 44 areas and 16 temperatures. The board was calibrated and tested. The complete set-up is ready to be assembled and will be tested in the third period. The interfaces and boundaries between stack, system and site were clarified and a new system concept for the integration of a 25-kW electrolysis stack based on hydraulic compression was developed. The delivery of the system to Air Liquide is scheduled for end of June 2023. A report about techno-economic analysis (TEA) and life cycle assessment (LCA) were developed. The development in the PROMET-H2 project will reach industrial levels.
PROMET-H2 shows strong potential to develop products beyond the state of the art. The best PROMET-H2 materials: catalysts developed by CSIC, CNR and CENMAT, were assembled (MEA). CENMAT scaled up highly active Ir supported on ATO keeping high quality. PROMET-H2 MEAS with the high perform low cost PTLs and BPPs developed by DLR will be the core in the novel stack developed by Propuls. PROMET-H2 stack will be tested in the last period of the project. A strong cost reduction maintaining efficiency and durability is expected outperforming the current SoA low temperature electrolysis. In the last period of the project the PEM electrolyser system will be installed at the AL site and real performance figures and results will be generated for a defined testing plan. Thereby the novel concept of hydraulic stack compression will be brought from laboratory scale to semi industrial scale at TRL5, an important step preparing further upscaling to MW scale foreseen for the years after projects end. An efficiency of at least 55.7 kWh/kg together with a considerably reduced CAPEX for the electrolyser will allow it to establish profitable power to fuel reaction pathways later on. Within the project the ability of the PEM electrolyser to provide gridservice as well as the further downstream conversion of CO2 with the hydrogen from electrolysis will be demonstrated. The sector coupling of power, gas and chemical market will enable energy storage and simplify the accommodation of surplus renewable energy in the electricity grids. The SME partners in the project are ambitious to commercialize the project results strengthening the European competitiveness in hydrogen technology
Scheme of the SS-mesh PTL with a plasma-sprayed coating
Container-based electrolysis system: division of the rooms
PROMET-H2 developed test cell for component testing hydraulic cell compresion
Performance and durability for PEMWE with Ir mixed oxides catalyst in anode (CSIC)
hydrometallurgical leaching method Monolithos
Segmented Cel Propuls
Interfacial contact resistance (ICR) of NbVPS/Cu-4 BPPs and experimental setup (embedded).
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