No single company dominates this dataset; filings are spread across established fuel-cell and materials firms, university research offices and a long tail of single-filing entrants. The most-cited record, US4214969A, covering a bipolar current collector-separator design, sits outside the modern electrolyzer field entirely but is still the reference point most later bipolar plate patents build on. Recent-year filing activity has thinned across almost every named assignee, so leadership by volume today looks different from leadership by citation influence.

Filings climbed steadily from 12 in 2017 to a peak of 64 in 2023, then eased back toward the 2022 level of 50, a pattern consistent with the core membrane electrode assembly and catalyst claim space becoming well populated rather than the technology losing commercial relevance. Because publication typically lags filing by roughly 18 months, the most recent one or two years in any such trend will always look lower than they eventually turn out to be once late filings publish. Readers should treat the tail end of any filing trend as a floor, not a ceiling.

This filing from the Korea Institute of Science and Technology describes a membrane electrode assembly built around an iridium oxide oxygen electrode layer electrodeposited onto a titanium diffusion layer, paired with a separate hydrogen electrode layer, with the electrolyte membrane's pores partially filling the titanium diffusion layer between them. That specific combination of an electrodeposited iridium oxide layer on titanium, plus partial pore-filling by the membrane electrolyte, is the structural detail a competing design would need to route around. It is a representative filing rather than a blocking generic claim over all MEA designs, so its scope is limited to that construction and preparation method.

The IPC composition shows dense filing in the core C25B electrolytic-production classification and meaningful overlap into fuel cell hardware and catalysis, but far thinner coverage in separation-membrane integration, water-treatment overlap and electroplating-adjacent claims. Degradation-rate diagnostics under real operating conditions, and oxygen-evolution catalysts that avoid iridium entirely, also show less claim density than the well-covered membrane electrode assembly space. These thinner branches are the more realistic places to file a defensible first claim, since the core MEA and bipolar plate space is already dense with prior art.

The raw trend suggests a plateau: filings peaked at 64 in 2023 and have not exceeded that since, and most named assignees in the recent-momentum data show zero filings in the latest tracked year, several down 100% year-on-year. That said, publication lag means the most recent year or two is always undercounted at the point of any data pull, so a lull in the visible data is not proof of a lull in actual R&D activity. The more reliable read is that the field has moved from rapid early filing into a steadier, more selective phase.