Water Electrolysis — Patent Landscape 2000–2024

Executive Summary

Water electrolysis and electrolytic hydrogen production, 2000–2024, at DOCDB family level.

The search profile behind this report — the CPC/IPC group C25B 1/02 (electrolytic production of hydrogen or oxygen) with its subtree, the photoelectrolysis group C25B 1/55, and the four groups retired in the 2021 edition that fed into C25B 1/04 — yields 33,424 DOCDB patent families with an earliest filing year between 2000 and 2024, covering 62,869 individual applications at 75 patent offices.

Filing activity rose from 122 families in 2000 to 4,354 families in 2022 — a factor of 35.7 and a compound annual growth rate of 17.6% over those 22 years. The curve is not smooth: annual filings grew by 47.6% between 2015 (701) and 2016 (1,035), and the 2015–2022 stretch alone runs at a 29.8% CAGR. Two thirds of the whole 25-year corpus — 21,738 families, or 65.0% — carries an earliest filing year of 2020 or later. The 2023 and 2024 counts (5,927 and 6,065) are provisional and will rise as publication catches up, so no growth figure in this report ends in those two years.

Geographically the field has one centre. 21,134 families (63.2%) include a filing at CNIPA, ahead of international PCT filings at WIPO (6,887; 20.6%), the United States (6,204; 18.6%), Japan (5,405), Korea (4,349) and the EPO (4,336). The Chinese share is a recent phenomenon: 524 families with an earliest filing year in 2000–2009 against 15,768 in 2020–2024.

By applicant sector the corpus splits almost evenly between companies (13,181 families; 39.4%) and universities (12,174; 36.4%). Read year by year, universities have filed more families than companies in every filing year from 2018 onwards except 2023, where the two are level (2,151 company against 2,146 university families); in 2024 the gap is 2,537 to 1,891. Technologically the corpus is concentrated in component work: 14,790 families touch electrodes (C25B 11/00) and 13,603 cell construction (C25B 9/00), against 1,252 families in high-temperature steam electrolysis (C25B 1/042) and 2,060 in photoelectrolysis (C25B 1/55).

Filing Trend 2000–2024

DOCDB patent families by earliest filing year. Each family is counted once, in the year of its earliest application, so the yearly values sum exactly to the 33,424 families in scope.

* 2023 and 2024 are provisional. Applications are published roughly 18 months after filing and reach PATSTAT later still, so the two most recent filing years in the Spring 2026 (patstat_2026a) edition are systematically under-counted and will rise. No growth rate in this report ends in a provisional year.

Top Applicants

The twenty largest harmonised applicant names (han_name) by DOCDB families in scope, 2000–2024. Applicants only (applt_seq_nr > 0); inventors are excluded.

Family counts run through filing year 2024. The two most recent filing years, 2023 and 2024, are provisional because of the roughly 18-month publication lag, so every portfolio figure in this section is a lower bound — most of all for the applicants whose activity starts after 2020.

Technology Sub-Areas

Where in subclass C25B the families in scope are classified. Counts are IPC-based and aggregated across all members of each family, at main-group level.

Inside the Scope Definition

The nine classification symbols that define the scope are not equally weighted. Families are counted once per symbol they carry in either scheme, so the column below sums above 33,424.

A family can be assigned to several classification symbols and to several main groups at once. Column totals in this section therefore exceed the distinct family count of 33,424 and must not be read as parts of a whole. All counts run through filing year 2024 and include the two provisional years 2023 and 2024, so each is a lower bound. C25B 7/00 (10 families) is listed in the data table but omitted from the chart, where it would not be legible.

Geographic Analysis

Where the families in scope are filed. Both cuts use the filing authority (appln_auth), which answers a market question — not where the applicant is based.

* The 2020–2024 band contains the two provisional filing years 2023 and 2024 and is therefore a lower bound for every office. Families are assigned to a period by their earliest filing year; a family filed at several offices is counted at each of them, so the column values are non-exclusive across offices and sum above 33,424.

Sector Analysis

Applicant sectors as classified by PATSTAT's psn_sector, at DOCDB family level.

A family with several applicants can belong to several sectors. The six values sum to 38,603 against 33,424 distinct families, so these are shares of the corpus rather than parts of a whole. This is why the breakdown is shown as a table and a line series, not as a pie chart.

Sector Development 2000–2024

* 2023 and 2024 are provisional filing years and will rise. The 2024 company value is below the 2023 value in the current data; that gap is consistent with publication lag and is not read here as a decline.

Growth Dynamics

Change in filing rate between 2016–2019 (four filing years) and 2020–2024 (five filing years). Because the two windows differ in length, the comparison is made on families per year, not on raw totals.

Entrants Without a Comparable Base

A second group of applicants had fewer than ten families in 2016–2019, so a rate multiple would be arithmetically unstable. Their absolute counts are reported instead:

• Huaneng Clean Energy Research Institute — 9 families in 2016–2019, 235 in 2020–2024
• China Petroleum & Chemical Corporation — 8, then 118
• PetroChina Company Limited — 2, then 107
• Huaneng Group Technology Innovation Center — 1, then 114
• North China Electric Power University — 1, then 70
• Linde GmbH — 8, then 57
• Schaeffler Technologies AG & Co KG — 7, then 59

* The 2020–2024 window contains the two provisional filing years 2023 and 2024, so both the later counts and the resulting multiples understate the true change. Applicants are counted by harmonised name; the fragmentation described in the Top Applicants section applies here too, which is why several large groups do not appear in this table under a single entry.

Collaboration Network

Co-filing between applicants. A family counts as co-filed when at least one of its applications carries more than one applicant.

5,824 of 33,424 families (17.4%) are co-filed. The co-applicant pairs behind that figure are not, for the most part, collaborations between independent organisations.

Pairs Across Different Applicant Names

Removing every pair whose two names share their leading word — which strips out the Huaneng, Toshiba, Mitsubishi and Sinopec self-pairings — leaves the following. Several of the remaining pairs still connect entities within one corporate group; that reading is an interpretation of the names, not a value returned by the query.

Grant Rate Analysis

Share of families with at least one granted application per office, restricted to the 2000–2020 filing cohort.

Across the whole corpus, 8,542 of the 13,827 families with an earliest filing year up to and including 2020 have a granted member — a grant rate of 61.8%. Families filed from 2021 onwards are excluded from every figure in this section: their examination is largely still running, and including them would measure examination speed rather than outcome.

Application Domains

Which other CPC subclasses the families in scope also carry. Labels come from the classification views, so the CPC-only Y sections appear alongside the ordinary technical subclasses.

The Y Sections as a Search Layer

Y02 and Y04 are CPC-only tagging schemes with no IPC counterpart, applied across the whole classification rather than within one field. For a climate-technology subject they are the obvious second search layer, and this report measured what they contribute before deciding whether to use them for scope.

• Volume. The group Y02E 60/36 — hydrogen production from non-carbon containing sources — together with its four retired subgroups matches 34,415 families with an earliest filing year in 2000–2024, more than the whole classification scope of this report.
• Reach beyond the core. 17,449 of those families carry none of the nine C25B symbols in CPC. That is an upper bound on what the Y layer would add, not the addition itself: the Y codes exist only in CPC, so the comparison can only be made on the CPC side, and part of those 17,449 families carry a C25B symbol in IPC and are already inside this report's scope. Adding the Y layer would therefore have grown the corpus by at most two thirds.
• Precision. A sample of 25 of those 17,449 families was read by title. 13 of 25 (52%) are not water electrolysis — photocatalytic water splitting without electrodes, covalent organic framework and carbon nitride photocatalysts, borane-based chemical hydrides, a biogas reactor and a hydrogen-enriched drinking-water device. That is what the group's own title says it covers: hydrogen from any non-carbon source, of which electrolysis is one example.
• No finer cut is available. The four retired subgroups Y02E 60/362 to Y02E 60/368, which subdivided that group before 2020, carry zero assignments in the family-level CPC table on this edition, so there is no electrolysis-specific Y symbol left to search.

Subclass counts are non-exclusive — a family carrying Y02E also sits in its ordinary technical subclass — so the column sums far above 33,424. All counts run through filing year 2024 and include the two provisional years 2023 and 2024, so each is a lower bound. CPC is assigned mainly by the EPO, USPTO and KIPO; 26,948 of the 33,424 families in scope (80.6%) carry a CPC code in subclass C25B, so this table under-represents the purely national Chinese and Japanese filings in the corpus.

Methodology

Search strategy, data basis, and known limitations.

Data basis as of 15 August 2026: EPO PATSTAT Global, Spring 2026 (patstat_2026a) on Google BigQuery, with classification labels and hierarchy from IPC edition 20260101 (in force 1 January 2026) and CPC edition 202608 (in force 1 August 2026). The classification set was completed in all three respects the classification methodology requires: every seed symbol was expanded to its subtree, the predecessor symbols from the 2021 C25B reclassification were unioned in, and retired symbols were kept rather than filtered out with is_active.

Report Files

This report consists of a metadata file (meta.json), a cover, a KPI strip, ten content sections and a contact section, plus queries.sql — the SQL actually executed for this analysis, carrying the PATSTAT and classification editions in its header. Anyone with access to PATSTAT Global on BigQuery can re-run those queries; on a later edition the figures will differ, which is why the edition is named on every page that carries a number.