For the energy transition from fossil-based to zero-carbon, renewable energy sources (e.g. solar and wind power) are a sustainable option. However, they are intermittent, and the energy they produced needs to be stored and reconverted. Water electrolysis produces hydrogen, which is a clean energy carrier, allowing large energy storage capacities and highly efficient reconversion to electricity via fuel cells. So far, 98 % of hydrogen is produced from fossil fuels, emitting every year megatons of CO2. Water electrolysis is therefore a clean and sustainable technology to produce hydrogen.
In particular, proton exchange membrane water electrolysis (PEMWE) allows to produce highly pure hydrogen, at higher current density, and can be easily coupled with renewable energy sources. This technology is not yet widespread because of the high cost and the low durability of the cell components over time, in particular the membrane with low mechanical strength when saturated, high permeation, and high creep at high load.
The aim of the HYDROGEN project was the reduction in the thickness of the PEMWE membrane, while keeping high mechanical stability and gas tightness, in order to reduce the voltage needed to produce hydrogen. The conventional membranes used for water electrolysis have thickness of 100-150 µm, which induces high ohmic drop thus reducing the performance of the device.
The approach employed was the reinforcement of perfluorosulfonic acid membranes by webs of polymer fibres prepared by electrospinning. The proton conductivity of such composite membranes was not impacted by the introduction of non-conducting fibres, which was reflected by the high electrochemical performance of the corresponding membrane-electrode assemblies with commercial electrodes/catalysts. The hydrogen permeation was lowered by a factor 3 and the mechanical resistance (breaking strength and elastic modulus) highly improved. Furthermore, the composite membranes presented higher stability in accelerated stress testing than a non-reinforced membrane with X1.5 lower voltage loss over time.
Further validation in an industrial environment is in progress with large membrane electrode assemblies (250 cm2) tested in a short stack. The experiments are still running, with the optimised composite membrane demonstrating so far higher durability than the non-reinforced membrane. The potential commercialisation of the fibre reinforced membranes for PEMWE application is appearing as a perspective.
