I expect you are thinking of hydrogen. It's not that we don't have plenty of ways to make it, indeed we do that, in vast quantities, to manufacture fertilizers, margarine etc. The problem is that we make it from natural gas, a fossil fuel, and there's no point to the fuel cell if it doesn't replace fossil fuel use. We can also make hydrogen by electrolysis, but that requires electricity, and therefore a way of making electricity, so doing that without burning fossil fuels becomes the issue.
hydrogen
A problem with fuel cell cars is that hydrogen is not readily available in pure form
Answer this question… One problem with fuel-cell cars is that ________ gas is not readily available in pure form.
hydrogen -apex :)
The adverb form is readily. Example sentence: All ingredients are readily available from a supermarket.
What gas is not readily available in pure form
Glucose is the energy that is locked inside an organic molecule most readily accessible in.
Which form of squash? The vegetable squash is readily available, as is the drink orange or lemon squash. The sport of squash is also played.
The W-4 form is readily available on the internet. The form is downloadable from the IRS directly at the following address: www.irs.gov/pub/irs-pdf/fw4.pdf
Halogens are highly reactive and readily form salts with metals.
Sodium Hydroxide is a solid white crystalline material commonly available in flake or bead form. It is also readily available in various solutions in water of varying concentrations.
The adverb form in 'readily'
Portable ice machines are fairly readily available from retailers like Walmart and Bed Bath and Beyond. They are also available online form retailers like Amazon.