HollowEL – Scaling Bubble-Free PEM Electrolysis with Hollow-Fiber-Based Direct Water Supply

Challenges

Green hydrogen production by water electrolysis is a key technology for the energy transition. However, current electrolysis systems still exhibit substantial energy losses and high investment costs. In PEM electrolysis, gas evolution can lead to bubble formation at catalytically active interfaces. These bubbles may block active surface areas, impede mass transport, reduce catalyst utilization, and contribute to unstable cell performance.

In addition, the complexity of water treatment, product-water recirculation, and cooling systems increases the cost and technical effort associated with conventional electrolyzer systems. To enable competitive, large-scale hydrogen production, more efficient, robust, and scalable cell concepts are required.

Objectives and project plan

In the HollowEL project, the partners are developing manufacturing processes for a novel PEM electrolyzer cell architecture. The approach is based on hollow fibers integrated into the polymer electrolyte membrane. Water is supplied directly to the membrane through these hollow fibers in a targeted, pressure-controlled manner.

The controlled water supply is intended to prevent both insufficient membrane hydration and the formation of a detrimental liquid film on the electrodes. This is expected to reduce gas-bubble formation and associated mass-transport losses. The functional principle, which has already been demonstrated at laboratory scale, will be further developed using application-relevant materials, larger cell formats, and scalable manufacturing processes.

Fraunhofer IGB is responsible for developing hollow-fiber membrane composites based on polymeric hollow fibers.

Impact

HollowEL will establish the technological basis for demonstrating bubble-free PEM electrolysis at high current densities under application-relevant operating conditions. By reducing bubble-induced mass-transport losses and enabling controlled water supply within the membrane, the approach has the potential to decrease the electrical energy demand of hydrogen production.

Furthermore, a simplified balance-of-plant design could reduce the requirements for water treatment, product-water recirculation, and active cooling. The project therefore supports the development of efficient, scalable, and resource-efficient electrolyzer technologies for the industrial production of green hydrogen.