coleafrado
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Joined: Fri Oct 11, 2019 11:58 pm

Re: Toyota Mirai Fuel Cell

Tue Mar 10, 2020 3:50 pm

mux wrote:
Tue Mar 10, 2020 5:41 am
The platinum problem in PEMFCs isn't just centered around the amount necessary for each PEMFC stack, it's really a cumulative problem tied into a particularly nasty speculative market:
- Each PEMFC has its counterpart in platinum used for electrolyzers
- PGMs in fuel cells are inherently a lot harder to recoup, as it's much more sparsely distributed and in the form of nanoparticles that tend to erode much more easily
- Platinum is a largely speculative market with centralized, tightly controlled supply that is hard to expand

We've seen in the early '00s that even the vague promise of future FC cars sent the platinum price up to ridiculous levels. That in turn actually made the platinum so expensive that fuel cell stacks became intrinsically uncompetitive in the long run, it was that bad - it went to over $2000/oz, which is about the total materials cost of a 100kWh battery - back then. It's gone down substantially now, to the point that you can theoretically make a ~100kW PEM fuel cell for less than the cost of a 100kWh battery, but imagine what the markets would do if some large automaker would decide to go 100% with fuel cells for the future.

Diesel cat converter platinum can be recouped 98%+, PEMFCs have much lower recovery rates, I think the best rates are still well below 50%. This is not completely intrinsic (i.e. this can be improved with better technology), but until we're at parity with other catalytic uses of platinum, we're going to need to supply the rest of the platinum with mined, new platinum. That's really what the speculation is all about. There's still a large technology gap enabling good platinum recovery AND low platinum usage at the same time. Keep in mind - Diesel cat converters may have the same total amount of platinum in them, but the total platinum demand from the catalytic converter industry is just 2% of their production capacity - the part they can't recover. That makes it a completely different ball game, for now at least.

TL;DR: the platinum discussion is more complex than raw materials amount, it's a quite unique combination of materials usage, recovery and speculative precious metal markets.
Neat. I guess Toyota is getting close to the minimum mass limit where there's so little platinum that physical erosion (not chemical poisoning) ends up being a large factor.

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