Alkaline Electrolyzer Patents: Who Leads, Where the Gaps Are 2026
- Filing has plateaued, not grown. 2024 was the peak year at 86 filings, but 2022 already sat near that level at 83 — this is a mature, not accelerating, claim space.
- Diaphragm patents dominate the citation graph. The five most-cited records in this dataset are all diaphragm or separator patents, led by a document cited 87 times — the technical bottleneck is membrane, not electrode, chemistry.
- China now files more than any single region. China accounts for 149 of the tracked records, ahead of the EPO at 142 and the US at 77, marking a shift in where alkaline electrolyzer IP is being built.
Filing growth compares 2021 (68 records) with 2024 (86) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 640 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
This dataset tracks patent families filed against zero-gap cell, diaphragm, electrode coating and Raney nickel claims within alkaline water electrolysis, indexed under C25B1/04 and related electrolytic-production subclasses. It spans filings from 2015 through the 2026 cut-off, covering 640 total records across six major receiving offices. The core claim territory sits in diaphragm construction and electrode coating rather than in cell architecture broadly.
Publication lags filing by roughly 18 months, so the 2025 and 2026 counts in any trend chart are undercounts of actual filing activity, not a real drop-off. Treat the last one to two years as provisional.
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Filing trends and technology composition
Two views of the same 640-family dataset: how filing volume has moved year over year, and which IPC subclasses the claims actually sit in.
Filing trend, 2017-2026
Filings rose from 28 in 2017 to a peak of 86 in 2024, with 2022 already at 83 — the growth curve flattened well before the peak year, and the 2025-2026 figures should be read as partial given publication lag.
IPC composition
Every record in this set carries a C25B classification by construction of the search, but secondary classifications spread into B01J catalysis (48), C08J polymer processing (47), H01M batteries and fuel cells (35), and B01D separation processes (34) — evidence that diaphragm and coating claims routinely reach into adjacent polymer and separation-science art.
Shares are the percentage of the 640 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
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Try EurekaThe documents anchoring this landscape
Diaphragm for alkaline water electrolysis, alkaline water electrolysis device, method for producing hydrogen, and method for producing diaphragm for alkaline water electrolysis
The diaphragm for alkaline water electrolysis according to the present invention comprises a porous polymer membrane, the porous polymer membrane comprising a polymer resin and hydrophilic inorganic particles. A porosity of the porous polymer membrane is 30% or more and 60% or less, average pore sizes at both surfaces of the porous polymer membrane is 0.5 μm or more and 2.0 μm or less, and a ratio of a mode particle size of the hydrophilic inorganic particles to the average pore size of the porous polymer membrane (mode particle size/average pore size) is 2.0 or more.Filed by Asahi Kasei Kabushiki Kaisha, published 2018-03-15 as US20180073155A1.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | WO2013183584A1 | Ion permeable diaphragm | 87 |
| 2 | JP2015117417A | Diaphragm for alkaline water electrolysis and alkaline water electrolytic cell using the same | 78 |
| 3 | WO2016148302A1 | Diaphragm for alkaline water electrolysis, alkaline water electrolysis apparatus, method for producing hydrog… | 60 |
| 4 | JP2013204146A | Diaphragm for alkaline water electrolysis and method for manufacturing the same | 54 |
| 5 | WO2016203701A1 | Diaphragm for alkaline water electrolysis, and method for manufacturing same | 44 |
| 6 | EP3085815A1 | Diaphragm for alkaline water electrolysis, method for producing same, and alkaline water electrolysis apparat… | 42 |
| 7 | EP3575442A1 | Bipolar electrolytic vessel, bipolar electrolytic vessel for alkali water electrolysis, and method for manufa… | 40 |
| 8 | EP3272908A1 | Diaphragm for alkaline water electrolysis, alkaline water electrolysis apparatus, method for producing hydrog… | 36 |
| 9 | JP2015117407A | Diaphragm for alkaline water electrolysis and method for producing the same, and alkaline water electrolysis … | 36 |
| 10 | US20150203976A1 | Bipolar alkaline water electrolysis unit and electrolytic cell | 34 |
Citation counts inside a searched corpus favour older filings — read this as a map of technical influence, not of current commercial priority.
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Browse MCP servers →What the numbers say about this field
Four read-outs from the filing, citation and classification data that matter for a freedom-to-operate or whitespace assessment.
Growth stopped several years before the peak
2022 filings already stood at 83, just three below the 2024 peak of 86. That flat trajectory across three years signals a claim space that has settled rather than one still expanding — new entrants are filing into occupied territory, not open ground.
Diaphragm patents anchor the prior art
All five of the most-cited records in this dataset claim diaphragms or separators for alkaline water electrolysis, topped by a filing cited 87 times. Any new membrane claim will be examined against this cluster first.
China has overtaken Europe and the US as filing venue
China's 149 records lead the EPO's 142 and the US's 77, with WIPO PCT filings at 60 and Japan at 54. A decade ago this field ran through Japanese and European diaphragm makers; the receiving-office data shows the centre of filing activity has moved.
Coating claims reach into catalysis and polymer art
Beyond the core C25B classification, the largest secondary subclasses are B01J catalysis (48) and C08J polymer processing (47). Electrode coating and diaphragm claims are being drafted, and likely examined, against catalysis and materials-science prior art as much as against electrochemistry art.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to alkaline electrolyzer alkaline electrolyzer, with the prior art for and against each one.
Who holds the ground, and where momentum has gone quiet
Ten identified co-assignee pairs point to a small set of collaborations, mostly between diaphragm specialists and electrolyzer integrators, that have shaped the strongest patent clusters. Recent-year filing counts, however, show almost no active momentum from any of the historically strongest names.
Diaphragm makers and integrators file jointly
The strongest co-assignee link in this dataset pairs a permanent-electrode diaphragm specialist with a heavy-industry electrolyzer integrator across 58 shared families, with a second pairing between the same diaphragm specialist and a national university at 56. Joint filing is the norm at the top of this field, not the exception.
The historically strongest filers have gone quiet
Several of the assignees with the deepest filing history show zero records in the latest tracked year, most with a -100% year-on-year change. That does not mean these organisations have exited the field — given the roughly 18-month publication lag, it more likely means recent filings have not yet published.
Even the most active recent filer is filing thinly
The single assignee with any latest-year activity in this dataset recorded just one filing, down 67% year on year. Read alongside the flat overall trend, this suggests incremental defensive filing around existing diaphragm and coating positions rather than a race for new claim territory.
| Assignee | Recent year | YoY |
|---|---|---|
| AGFA-Gevaert N.V. | 1 | -67% |
| De Nora Permelec Ltd. | 0 | — |
| Kawasaki Heavy Industries, Ltd. | 0 | -100% |
| Asahi Kasei Corporation | 0 | -100% |
| Yokohama National University | 0 | -100% |
| Industrie De Nora S.p.A. | 0 | -100% |
| Nippon Shokubai Co., Ltd. | 0 | -100% |
| thyssenkrupp Uhde Chlorine Engineers GmbH | 0 | — |
Where to take this analysis
The dataset points to specific next steps depending on whether you are clearing a design, tracking competitors, or scoping new claims.
Run a freedom-to-operate check against the diaphragm cluster
Before finalising any membrane or separator design, check it against the five most-cited diaphragm records in this dataset directly — they carry the deepest citation trails and the broadest claim scope.
Explore diaphragm claims in EurekaWatch for the publication-lag catch-up
The 2025-2026 filing counts will rise as pending applications publish. Re-run this landscape in six to twelve months to see whether the plateau observed since 2022 holds or breaks.
Set up a filing alert in EurekaScope claims into the under-claimed branches
Zero-gap sealing, Raney nickel regeneration and bipolar plate coatings show comparatively thin dedicated coverage relative to diaphragm art. These are worth a deeper novelty search before committing R&D budget.
Search white space in EurekaCommon questions about alkaline electrolyzer patents
The most-cited records in this dataset are diaphragm and separator patents, led by a filing cited 87 times, with the next four most-cited documents also covering diaphragms for alkaline water electrolysis. Strong co-assignee links exist between diaphragm specialists, heavy-industry integrators and university research groups, with the strongest pairing sharing 58 families. This concentration means diaphragm construction, not electrode or cell-housing design, is the area with the deepest and most defensible prior art.
Filing volume rose steadily from 28 records in 2017 but had already reached 83 by 2022, close to the eventual peak of 86 in 2024. That flat trajectory across several years indicates the field has plateaued rather than accelerated, even before accounting for the roughly 18-month lag between filing and publication that understates the most recent years. Anyone benchmarking growth should treat 2025 and 2026 figures as provisional rather than as evidence of decline.
The dense citation cluster sits in diaphragm and separator design, so a new entrant filing there faces the heaviest prior art. Comparatively thinner coverage appears in zero-gap cell sealing methods, Raney nickel electrode regeneration, bipolar plate corrosion coatings and diaphragm pore-size gradient control — branches adjacent to the core cluster but without the same density of dedicated records. A targeted novelty search in these areas is a more efficient use of drafting effort than competing directly on membrane composition claims.
China leads with 149 records in this dataset, ahead of the European Patent Office at 142 and the United States at 77, with WIPO PCT filings at 60 and Japan at 54. This marks a shift from a field historically anchored in Japanese and European diaphragm manufacturing toward a broader, China-weighted filing footprint. Companies assessing regional freedom-to-operate risk should treat Chinese-office filings as a primary rather than secondary search target.
US20180073155A1, filed by Asahi Kasei Kabushiki Kaisha and published 2018-03-15, claims a porous polymer diaphragm membrane with porosity between 30% and 60%, average surface pore sizes between 0.5 and 2.0 micrometres, and a defined ratio of hydrophilic inorganic particle size to pore size of 2.0 or greater. A design that falls outside any one of these numeric ranges, or that uses a materially different particle-to-pore relationship, sits outside this specific claim, though it would still need checking against the other highly-cited diaphragm records in this dataset. It is a representative example of how tightly diaphragm claims in this field are drawn around specific physical parameters rather than broad functional language.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.