The challenge is cost of energy production, which translates directly into cost per mile when it comes to hydrogen powered vehicles. That matters because when the choice is pay 1x or 3-5x per mile, it's going to be an easy choice for most and hydrogen is going to lose every time. Hydrogen is simply too expensive per mile relative to other options.
That's why battery EVs are so popular; they are clearly cheaper to drive per mile. Especially if you charge them cheaply from your own solar panels, using off peak grid rates, etc. You are basically driving almost for free. In some cases grid operators literally pay consumers to plug their cars in so they can offload excess energy. It's cheaper than shutting down gas powered peaker plants and having to restart them a few hours later.
The article is interesting because it proposes a way that gets production to less than 2x the efficiency difference relative to using solar panels to generate energy in terms of efficiencies (12-15% vs 20-25%). That's impressive. However, it says nothing about the cost of hydrogen because this is an academic article and not an actual product. However it suggests an improvement. For reference, producing hydrogen from wind energy would use about 3-4x the kwh in generated electricity to produce 1kwh of hydrogen.
That's not bad. But even (wrongly) assuming all of that would be converted to motion, that would be about a 3x cost per mile difference already vs. just putting the wind energy straight in your battery. Burning hydrogen has inherent inefficiencies (you produce heat and noise) similar to burning other fuels (20-30% efficiency would be pretty good). And even fuel cells are not that efficient; 60% efficiency is pretty good apparently. And if you are using hydrogen for fueling vehicles, what matters is the cost per mile. So, on top of the production that would be another loss of about 1.5 - 5x on top of the production inefficiencies.
The fantasy of hydrogen in cars and trucks is that it is needed and that the cost doesn't matter. The reality is that there are battery equipped vehicles in almost every weight and vehicle class being produced already with pretty awesome cost per mile that are going to be pretty hard to compete with using hydrogen. It's a no-brainer choice already for a lot of drivers and fleet operators. Sure, their range is not always that impressive. But at about 3-5x the cost per mile difference that's an inconvenience that can be worked with.
The other fantasy is that hydrogen is carbon neutral. The vast majority of hydrogen produced is grey hydrogen. If you want to save some carbon, fuel your car using methane instead of hydrogen. You'll produce a lot of co2 but a lot less than when you use that methane to produce hydrogen which you then burn or use in a fuel cell. That's the sad status quo of hydrogen on the road right now. What little there is neither green, efficient, or cheap. Making it green will raise the prices. Making it less inefficient is going to be a long battle, and until that is done, it will be inherently more expensive.
Green hydrogen when production of that is going to be more meaningful is still going to be useful elsewhere (aviation, shipping, heavy industries). And with wind and solar intermittency that basically means there are going to be surplusses (rather than shortages) because people will over provision to compensate. Hydrogen is a great way to use such excess energy. There's going to be plenty of demand for it. Just not on the road.