Röntgenmikroskopaufnahmer einer Membran-Elektroden-Einheit (MEA)

grELjet – Graded Catalyst Layers for PEM Electrolyzers

As part of the grELjet project, ZBT is collaborating with Fraunhofer ENAS to develop spatially resolved, optimised catalyst layers designed to reduce the iridium requirements of PEM electrolysers and increase their efficiency.

Iridium is a particularly scarce and expensive raw material used in the anodes of polymer electrolyte membrane electrolysers. grELjet is investigating how inkjet printing can be used to precisely apply this precious metal exactly where it is most utilised within the electrode.

Stable Catalyst-Based Inks for Inkjet Printing

The process is based on stable, printable ink systems consisting of iridium as the active material, an ionomer, and various solvents. The study focuses on ternary systems composed of water, a high-boiling-point solvent such as DMSO or 1,2-ethylene glycol, and N-propanol.

Among other things, ENAS characterises the stability, viscosity, and other properties of inks that are relevant to inkjet printing.

Selected inks have already been scaled up from 10 to 40 milliliters. Fraunhofer ENAS used these inks to fabricate PEM electrolysis anodes with variable catalyst loading via inkjet printing by directly coating the membrane.

ZBTriangle: Browser-based tool for ternary solvent systems

With ZBTriangle, the ZBT has developed an interactive browser-based tool for planning, visualising, and documenting ternary solvent systems. Three-component compositions can be defined directly in the ternary diagram, limited by minimum and maximum values, and saved for screening series.

In particular, the tool supports the development of catalyst, ionomer, and binder inks, as well as the investigation of solvent mixtures with regard to dispersion, wetting, and coatability. Experimental properties such as stability or viscosity can be assigned to the compositions and displayed as a heat map or color-coded data points.

ZBTriangle requires no installation, runs directly in the browser, and is publicly available. Data and charts can be exported for further analysis and imported again.

go to the Triangle tool on GitHub

Using Iridium in a Targeted and Location-Specific Manner

At the ZBT, the directly coated catalyst membranes are assembled into membrane-electrode assemblies and electrochemically characterised. The initial results are on the same order of magnitude as comparable values reported in the literature and demonstrate the potential of inkjet printing for the production of directly coated membranes.

In the next step, the project will develop spatially resolved gradient concepts within the catalyst layer. Simulations will be used to identify areas where different catalyst loadings or layer properties are particularly advantageous. The goal is to use iridium in a more targeted manner without compromising the electrolyser’s performance. In the long term, this approach can help reduce material costs and increase the efficiency of PEM water electrolysis.

Project information

  • Project Acronym: grELjet

  • Project Title: Improving Efficiency and Reducing Costs Through Graded Catalyst Layers for Polymer Electrolyte Membrane Electrolyzers Using Inkjet Printing for Spatially Resolved, Functionally Optimized Precious Metal Deposition

  • Term: 1 December 2025, through 31 May 2028

  • Funding Program: Industrial Collaborative Research (IGF)
  • Grant ID: 01IF24611N

  • Total grant amount: 523,426 €

  • Project partners:

    • Fraunhofer Institute for Electronic Nanosystems ENAS

    • ZBT – The Hydrogen and Fuel Cell Center GmbH

Contact

Wladimir Philippi
Electrochemical Components
+49 203 7598-3129
Portrait of Wladimir Philippi

Skills

The project builds on the ZBT’s extensive expertise in the fields of electrolysis, electrochemical components, materials and ink development, and electrochemical characterisation. The existing infrastructure enables the development, fabrication, and evaluation of membrane-electrode assemblies and catalyst layers under real-world conditions. This expertise and infrastructure are also available to industry partners through development services and contract research.

  • Development Services – Development and optimisation of electrochemical components, materials, and processes for electrolysers and fuel cells.
  • Measurement and Testing Services – Electrochemical characterisation and evaluation of components and systems under defined and real-world operating conditions.
  • Modeling and Simulation – Modeling and simulation of electrochemical processes and components for the analysis and optimisation of electrolysis and fuel cell systems.

 

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