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

Periodic Reporting for period 1 - PROMET-H2 (Cost-effective PROton Exchange MEmbrane WaTer Electrolyser for Efficient and Sustainable Power-to-H2 Technology)

Reporting period: 2020-04-01 to 2021-09-30

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.
The achievements of the recent period are related to the initial testing of the developed membranes and catalysts deployed inside novel MEA. Highly efficient and durable membrane electrode assemblies have been developed by integrating novel electrocatalysts with low CRM materials with new durable membranes and will impact the next generation of components for PEM electrolysers. The tested CRM-free catalysts were Molybdenum disulfide (MoS2) on black pearl carbon (CSIC), Molybdenum carbide for the hydrogen evolution reaction (HER) (CENMAT), and silver on titanium suboxide (CNR) for the oxygen evolution reaction (OER). Moreover, catalysts dedicated to a CRM reduction, namely molybdenum carbide decorated with platinum (CENMAT) for HER and iridium deposited on antimony tin oxide (ATO) (CENMAT). The Ir mixed oxide (CSIC) and Ir on ATO (CENMAT) were tested with a remarkable reduction of Ir. Chemours has developed a novel membrane (80 µm thickness) showed remarkably lowered H2 cross-over (ca. 0.2% H2 in O2) compared to already commercially available NR212 membrane (ca. 0.6% H2 in O2) and was able to fulfill the PROMET-H2 target of < 2% H2 in O2 at 0.5 A cm-2. Together with the results from the loading reduction regarding commercially available IrO2 (0.2 mgIrcm-2) and Pt/C (0.1 mgPtcm-2) it seems to be possible to meet the PROMET-H2 target for MEA with reduced CRM content in the next period. A sensitivity study with results to the components that constitute the MEA was carried out. CNR, DLR and FZJ work in the integration of the novel catalyst developed in the WP1.
In addition, in the project, MONOLITHOS develops a low cost and simple recycling process, that allow 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. 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 coated with Pt or Au. Referring to the CRM free BPP, Mo dense coating was applied on SS-BPP and it is currently under study. For porous transport layers (PTL) stainless steel meshes were prepared and coated (Nb/Ti) at DLR using the plasma-spray, producing a microporous layer structure (MPL). Reduction of cell voltage and protection from corrosion were demonstrated. The developments were supported by many characterization methods to determine physical properties.
According to the project plan new PEMWE test cells with 25 cm² active area based on the patented hydraulic cell compression system were designed, built, pre-tested and delivered to the research partners for component testing and material screening. The major work on the design for the Baseline Stack as well as for the PROMET-H2 prototypic stack is done. In parallel, the WP4 partners started to prepare an experimental investigation of current density and temperature distribution in-situ of a laboratory stack. The interfaces and boundaries between stack, system and site could be clarified and a new system concept for the integration of a 25 kW electrolysis stack based on hydraulic compression was developed. This included measures for precise control between gas pressure and contact pressure. The official approval process could be launched and a testing plan with different protocols was defined.By collecting the numbers that will be used as a basis for the following techno-economic analysis (TEA) and life cycle assessment (LCA). The development in the PROMET-H2 project will reach industrial levels.
In the first period 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, membranes developed by Chemours will be assembly by FZJ (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 integrated in the novel stack developed by Propuls. PROMET-H2 stack will be tested in the second period of the project. A strong cost reduction maintaining efficiency and durability is expected outperforming the current SoA low temperature electrolysis. In the second half 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
PROMET-H2 developed test cell for component testing hydraulic cell compresion
hydrometallurgical leaching method Monolithos
Performance and durability for PEMWE with Ir mixed oxides catalyst in anode (CSIC)
Container-based electrolysis system: division of the rooms
Interfacial contact resistance (ICR) of NbVPS/Cu-4 BPPs and experimental setup (embedded).
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