This dataset identifies 50 patent families published between 2015 and 2026 that combine alkaline electrolyzer or alkaline water electrolysis terminology with green-hydrogen framing, within the core C25B1/04, C25B15 and C25B9 classification codes. That is a narrow slice of the broader hydrogen-production patent universe, since it excludes PEM and solid-oxide electrolysis filings by construction. Filing activity was minimal before 2022 and only reached double digits in 2025, so the total will keep growing as later filings publish.

No single assignee dominates this corpus; the 50 families are spread thinly across research institutes, oilfield-services groups, industrial gas companies and one Turkish membrane specialist. Every assignee with prior filing history shows zero activity in the most recent tracked year, which is a sign of a field still being entered by first-time or single-cycle filers rather than one with an established leaderboard. Co-filing is also rare, limited to two pairs in the whole dataset.

WO2024005740A1 claims a specific alkaline electrolyzer separator membrane: a woven or non-woven PPS base coated with a kaolin/kaolinite-and-alumina mullite aluminium silicate layer, applied using PSU, PVDF and PTrFE binders combined with Aloe vera-derived compounds. It does not block separator work generally — it blocks that specific mineral-coating-plus-plant-extract-binder combination and close variants. Separator approaches using different base polymers, different mineral coatings, or synthetic-only binder systems sit outside its claim scope.

The trend is uneven rather than steadily rising: filings were near zero through 2017, sat at just 3 families at the 2022 midpoint, then jumped to a peak of 20 in 2025. Because publication lags filing by around 18 months, the 2026 figure of 2 families understates actual filing activity for that year and should not be read as a decline. The honest read is that 2025 marked a genuine acceleration, but one data point is not enough to call it a sustained trend yet.

The clearest under-claimed ground sits in dynamic, renewable-coupled load-following control and in bifunctional separator/desalination membranes — both appear as secondary themes rather than dense claim clusters in this corpus. Alkaline electrolyte-catalyst co-optimisation for intermittent power input is similarly thin. Core electrolytic-cell hardware claims under C25B are comparatively well-occupied, so new entrants are more likely to find open ground in the control-and-materials periphery than in the cell itself.