I hadn't realised until very recently that most hydrogen produced comes from coal: https://www.google.com/amp/s/theconversation.com/amp/explain...

Most of the time it isn't a green fuel at all and is just a way to keep mining coal.

That is not correct. Globally 75% of hydrogen is produced from Natural Gas:

https://www.iea.org/reports/the-future-of-hydrogen

See section on production.

The most commonly used process creates a mixture of steam, hydrogen and CO2. The water is condensed and the CO2 removed to purify the hydrogen product. The CO2 is a concentrated stream. This is sometimes captured and sold as a byproduct (eg food grade CO2 for beverages or dry ice).

The gas based production is no better because of the CO2 emissions of course.

There is a promising electrolysis route as well now, zero emissions:

https://newatlas.com/energy/hysata-efficient-hydrogen-electr...

As with all promising research papers, believe it when you see it in commerical-scale use.

In the past most catalyst improvements have run into problems with maintenance.

Electrolysis powered by nuclear energy seems very clean and green to me.

With the added benefit of not requiring an overhaul of the electrical grid to be able to handle everyone charging their cars.

Instead of overhauling the electrical grid, gas stations just have to maintain cryogenic pressure tanks?

Exactly, my money would be on an inert storage format - if you could mass produce hydrogen and keep it around safely inert (with low energy cost to convert it back), EVs would be beat so bad in the long run it wouldn't even be funny...

EVs are nice in short term but battery issues like these illustrate their (should be obvious) shortcomings.

WRT to this battery technology, ironically the same sector being targeted by hydrogen might benefit, i.e. rail tech - if you stick a high number of cheap batteries onto a large, heavy motorcar, the energy differential is almost negligible as you make up for it in part through momentum, but also just scale (more passengers transported per watt, more charge available per trip).

Producing hydrogen directly from nuclear plant is being developed. https://www.iaea.org/topics/non-electric-applications/nuclea...

If you are doing electrolysis then solar/wind is a much better option than nuclear.

Much lower up front investment and none of the huge downsides of nuclear.

It might be green jut it is super expensive and not very green for the decade it takes to build a plant.

As opposed to how green it is to build a solar or wind farm?

This is true, but hydrogen cars at scale are still more practical than historical fossil fuel approaches.

Luckily we have an even better option available for transport so we can focus green hydrogen on replacing all the other uses of fossil fuels.