Proton exchange membranes
Three patents explore improvements to proton exchange membrane water electrolysers.
Proton exchange membrane (PEM) water electrolysis uses electricity to dissociate water into hydrogen and oxygen. A proton-conducting polymer membrane separates the electrodes and transports protons between them, enabling low-carbon electricity to be converted into hydrogen as a storable energy carrier.
The compact design and high-purity hydrogen output are attractive, but deployment remains constrained by cost and efficiency. Key challenges include the typically sluggish oxygen-evolution reaction and reliance on scarce iridium (Ir)-based catalysts to achieve sufficient catalytic activity and long-term stability.
Three recently granted patents describe innovative approaches to reducing precious-metal requirements and improving catalyst usage in PEMs.
US 12,612,704 B2, granted to Plug Power Inc., USA, in April 2026, addresses problems associated with employing Ir or iridium oxide to catalyse the oxygen evolution reaction.
In particular, conventional unsupported catalysts often agglomerate and become non-uniformly distributed, requiring comparatively high iridium loadings. In contrast, metal-oxide particles used in supported catalysts can be difficult to decorate uniformly with Ir nanoparticles.
The patent claims protection for a catalyst comprising a support formed from a plurality of support particles and catalyst particles. Each support particle has a surface that comprises at least one metal oxide, at least one dopant attached to the metal oxide, and at least one organic group attached to the metal oxide through a diazonium-salt reaction. The catalyst particles are specifically either IrCl62- or Ir+.
According to the patent, the diazonium-salt reaction covalently functionalises the metal-oxide surface with the organic group. This enables the support particles to be loaded with Ir-based catalyst particles. For example, the organic group may be substituted with functional groups that are positively charged to attract IrCl62-, or negatively charged to attract Ir+.
Such an electrostatic interaction promotes a more homogeneous distribution of Ir across the support and reduces the average Ir particle size. This makes more of its surface available for the oxygen evolution reaction per unit mass, potentially reducing the need for precious-metal loading while improving catalytic mass activity.
Patent US 12,371,804 B2, granted to the Netherlands Organisation for Applied Scientific Research in July 2025, also addresses a barrier to the use of expensive Ir, ruthenium and platinum catalysts in PEM water electrolysers.
In particular, as catalyst content is reduced, interruptions or discontinuities within the catalyst layer can occur and small regions or patches can become electrically isolated from one another and from porous transport layers, resulting in poor catalyst utilisation.
The patent claims protection for a PEM-based electrolyser that comprises an anode, a cathode and a PEM.
The anode and cathode each comprise a catalyst layer positioned between a porous transport layer and the corresponding membrane surface.
The electrolyser additionally contains a conductive first mesh foil and/or a conductive second mesh foil stacked on the respective anodic or cathodic catalyst layer, forming a conducting interface with it. Each mesh foil is positioned either between the relevant catalyst layer and the membrane, or between the catalyst layer and its porous transport layer.
According to the patent, the conductive mesh foil provides an additional lateral, or in-plane, electrical pathway. It functions as a conductive shunt between otherwise disconnected catalyst regions, allowing them to exchange electrons with the rest of the electrode and participate in electrolysis. This increases the effectively utilised catalytic area and reduces Ohmic resistance, without requiring an increase in precious-metal loading.
Patent EP 4578995 B1, granted to Fundació Institut de Ciències Fotòniques, Spain, in May 2026, proposes a different solution – an anode catalyst that is platinum group metal (PGM) free.
It is made from a delaminated metal oxide represented by ABxOy, with x=1 or 2 and y=2, 3 or 4, where A is selected from non-platinum group transition metals and B is from chalcogen elements and transition metal group VI elements.
The patent also claims a method for preparing the catalyst. This involves immersing a metal oxide in an aqueous base solution, continuously stirring to obtain a delaminated product, and then washing, centrifuging and annealing the product.
According to the patent, the base treatment partially leaches the sacrificial B-containing oxyanions from the crystalline oxide, generating vacancies that can be filled by water or hydroxide species. The inventors find that water and water fragment trapping and stabilisation in the delaminated catalyst enables improved oxygen-evolution kinetics, while providing stability under the strongly acidic conditions found at the anode.
The patent reports the first successful implementation of a PGM-free catalyst in a PEM electrolyser at a current density of 1A/cm2 under industrially relevant operating conditions.
