Guide · updated 2026-09-11
How to evaluate a low-iridium catalyst claim
A checklist for reading a PEM OER catalyst paper or supplier pitch: current density, Tafel slope, stability window, and what is usually missing.
Iridium-loading reduction attracts more research and patent activity than almost anything else in green hydrogen catalysis, so you will read a lot of these claims. Most are honest and narrow. The failure mode is usually in what gets omitted rather than what gets stated.
The checklist
1. At what current density was activity measured? If the answer is 10 mA/cm², you are two decades below commercial operation. Ask for the Tafel slope so the number can be extrapolated, and treat the extrapolation as uncertain.
2. What is the Tafel slope? Across two decades, 40 mV/dec versus 60 mV/dec is a 40 mV difference in the extrapolated result. A claim without a slope cannot be compared to anything.
3. Grams per kilowatt, not percentage reduction. Percentages need a baseline, and baselines vary enormously. Intensity in g/kW is comparable across designs and is the number that matters at scale.
4. What were the stability conditions? Acidic OER at potential is the destructive condition. A durability test at low current density is a much weaker claim than one at operating current density, even if it ran longer.
5. Is the support included in the accounting? Some low-loading results depend on a support or a structure that is itself expensive, fragile, or not manufacturable at area. The catalyst is not the whole cost.
6. What happened to the cell voltage? The honest version of a loading-reduction claim reports what it cost in overpotential. A claim that reports neither a voltage penalty nor a stability penalty is usually incomplete rather than miraculous.
What to do with a claim that passes
Convert it. Take the reported overpotential to your operating current density with the overpotential converter, then put the result and the loading into the LCOH calculator with your electricity price.
A claim that looks impressive at 10 mA/cm² sometimes turns out to be worth a few cents per kilogram. Occasionally one turns out to be worth a great deal. Either way you will know which, which is more than the abstract told you.
Questions
What is the single most common problem with these claims?
Reporting activity at 10 mA/cm² and leaving the reader to assume it holds at 2 A/cm². That is a two-decade extrapolation, and whether it holds depends on the Tafel slope and on whether the mechanism changes.
How long a stability test is meaningful?
There is no universal answer, but a few hundred hours at low current density tells you much less than a shorter test at realistic current density and potential. Ask what current density the durability test ran at, not just how long it ran.
Does a percentage reduction in iridium mean much on its own?
Not without the baseline. A 70 % reduction from an unusually high loading can still land above a competitor's starting point. Ask for grams per kilowatt, which is comparable across designs.
Put a number on it
The LCOH calculator turns any of this into euros per kilogram. Free, no account.
Open the calculator