SDE produces hydrogen at significantly lower energy input than conventional water electrolysis by oxidising SO₂ at the anode while generating hydrogen at the cathode. Finding the right membrane is critical: it must conduct protons efficiently while limiting unwanted SO₂ crossover that reduces system efficiency.

In the study, Cellfion's membrane was tested head-to-head with two conventional membrane types over two days of electrolysis followed by a 15-hour continuous stability run. The results were clear: Cellfion's membrane achieved the lowest specific energy demand among all membranes tested, averaging 37 kWh/kg of gas produced in the long-term run, compared to 49 kWh/kg for the leading fluorinated benchmark. Gas production with the Cellfion membrane also exceeded that of conventional alternatives over the 15-hour period, with output continuing to improve as the run progressed.

The performance advantage comes down to membrane architecture. Where fluorinated membranes rely on water-filled channels that allow SO₂ molecules to pass through alongside protons, Cellfion's phosphorylated cellulose nanofibrils create a network that limits SO₂ crossover and the parasitic reactions it causes, while maintaining solid proton conductivity throughout operation.

Critically, the study also confirmed that both SDE configurations, with Cellfion and with the fluorinated benchmark, required less energy than conventional water electrolysis, validating SDE as an industrially viable route to hydrogen. With upcoming EU REACH regulations tightening restrictions on PFAS and fluorinated chemicals, the case for a cellulose-based, fluorine-free alternative is no longer just environmental — it is regulatory and operational.

The research was conducted as part of the EU Horizon HySelect project and marks an important external validation of Cellfion's membranes in a demanding electrochemical application.

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https://www.sciencedirect.com/science/article/pii/S0360319926020896