Membrane-Free Electrolysis Boosts Green Hydrogen Production and Sustainable Plastics Precursors

Researchers at Keele University in Staffordshire, England have designed and tested a membrane-free alkaline paired electrolyzer that co-produces hydrogen and 2,5-furandicarboxylic acid (FDCA), according to a recent institutional announcement.

Challenging Conventional Alkaline Electrolysis

Conventional alkaline water electrolysis drives hydrogen evolution at the cathode and oxygen evolution at the anode, and it depends on a diaphragm or membrane to prevent gas crossover. That oxygen-evolution reaction is energetically demanding and yields a low-value co-product, says Charles E. Creissen, lead author and Senior Lecturer in electrochemistry at Keele. It also necessitates a costly separator to maintain hydrogen purity and system safety. In short, the anodic oxygen step raises energy demand and hardware complexity.

Reinventing the Anode Reaction

Rather than evolve oxygen, the Keele team replaces the anodic half-reaction with electrochemical oxidation of 5-hydroxymethylfurfural (HMF) into FDCA, a bio-based building block for polyester and related polymers. At the cathode, water reduction generates hydrogen. By omitting the oxygen-evolution step, the cell no longer produces oxygen gas at the anode and thus can operate without a membrane or separator, according to Keele University. That change removes both the need for a gas barrier and the resistive losses associated with it.

Membrane-Free Alkaline Paired Electrolysis

In the reported configuration, an alkaline electrolyte carries hydroxide ions between electrodes. At the anode, biomass-derived HMF molecules undergo a series of oxidation steps to form FDCA, while at the cathode water molecules are reduced to hydrogen gas. According to the research abstract, this membrane-free cell reached a current density of 0.5 A cm⁻² and a full-cell voltage below 1.5 V under laboratory conditions. Those laboratory metrics suggest a lower energetic penalty compared with an oxygen-evolving anode, at least in short-duration tests.

The study was listed with DOI 10.1021/acselectrochem.6c00218 in ACS Electrochemistry, according to the American Chemical Society, and follows a working‐paper version posted on ChemRxiv in December 2025. The published record and the preprint together document the experimental setup, the electrochemical data and the FDCA yields reported by the authors.

Dual-Product Strategy and Potential Advantages

Co-producing hydrogen and FDCA could help address two limitations of conventional alkaline electrolyzers. First, replacing oxygen evolution lowers the cell voltage under suitable catalyst and operating conditions. Second, generating FDCA—a potential precursor for polyethylene furanoate—adds a valued chemical stream rather than low-value oxygen, says Lewis S. Cousins, PhD researcher and co-author. In other words, the system turns what is normally a wasted anodic product into a potentially valuable feedstock.

Keele University highlights that its HMF feed is derived from food-waste-derived molecules and that renewable electricity powers the cell. The membrane-free design may simplify hardware by eliminating a corrosive, resistive component and could reduce balance-of-plant complexity, according to the institutional announcement. Those design features point to fewer parts to maintain and to potentially lower parasitic losses in a scaled system.

Lab-Scale Demonstration, Commercial Hurdles

Despite promising performance metrics, this work remains a research-stage proof of concept. It does not establish continuous operation, long-term catalyst stability, product purification, or an industrial hydrogen cost advantage. The International Energy Agency continues to identify electricity price, financing and uncertain demand as barriers to low-emissions hydrogen, indicating that reducing cell voltage addresses only one part of overall system economics. Put bluntly: a lower cell voltage helps, but it is not a complete solution to the cost and market challenges that determine commercial viability.

Key scale-up challenges include securing a reliable HMF supply, developing robust electrocatalysts, designing flow cells for effective gas management without membranes, and implementing downstream FDCA separation. Hydrogen purity requirements and alkaline-electrolyte handling remain critical safety and operational considerations. Each of those elements will need targeted engineering and supply-chain planning before pilots can transition to industrial demonstrations.

Context in Power-to-Chemicals Research

Researchers have long explored paired or assisted electrolysis, where the anodic oxygen evolution is replaced by oxidation of organic feedstocks. HMF has emerged as a leading candidate because it can be sourced from carbohydrate streams and yields FDCA under alkaline conditions. Earlier studies demonstrated HMF oxidation with hydrogen evolution in divided cells and membrane-electrode assemblies. The Keele work is distinct in combining HMF-to-FDCA chemistry with a fully membrane-free alkaline configuration. That distinction matters because it changes how designers approach reactor layout, product separation and safety systems.

Economic and Environmental Outlook

FDCA is a potential bio-based replacement for terephthalic acid in polyesters. Co-production with hydrogen could improve electrolyzer economics if FDCA commands a stable market price, according to analysts. Environmental benefits hinge on life-cycle factors including the source of renewable electricity, land and water use for biomass, catalyst materials, and energy inputs for FDCA purification. In practice, the net impact will depend on supply chains and the efficiency of downstream processing as much as on the electrolyzer itself.

If realized at scale, membrane-free paired electrolysis might encourage integrated designs where hydrogen fuel production and chemical synthesis occur in a single unit. That integration echoes broader trends in sustainable energy, industrial decarbonization and circular-economy approaches. Still, converting laboratory proof of concept into industrial equipment will require resolving material durability, product separation and continuous-flow operation.

Looking Ahead

The Keele team’s membrane-free electrolyzer offers a novel blueprint for green hydrogen production coupled with biomass valorization. Next steps will involve demonstrating continuous‐flow operation, verifying catalyst lifetime, optimizing electrode spacing and reactor geometry, and delivering pure FDCA suitable for polymer manufacturers. While this configuration isn’t yet commercially ready, it underscores emerging pathways to couple hydrogen production with valuable chemical outputs, advancing both green hydrogen production and sustainable energy goals.