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Various gasses are currently used to transport and store energy for heating and electricity generation.

Most of them contain carbon:
Methane, propane, butane, carbon monoxide and natural gas.

It could be of advantage to use gasses that do not contain carbon.
One example for that is hydrogen.

Are there other gases that theoretically could be used, if they could easily be created?
I assume most can not practically used because they are not trivial to generate, but I like to ignore that, and assume they can be created.

Are there other gases that could be used, in principle, as energy carrier?

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    $\begingroup$ Ammonia is a possibility, but not particularly practical. Various hydrazines, such as those used as rocket fuels. Also not so practical for various reasons. $\endgroup$
    – Ed V
    Feb 16, 2020 at 3:41
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    $\begingroup$ I should say that hydrazine itself meets your criteria, but it is quite toxic and unpleasant. The rocket fuel derivatives, such as UDMH (unsymmetrical dimethyl hydrazine) have carbon. But maybe there are amino-hydrazines or hydroxy-hydrazines. You may also enjoy reading John D. Clark’s wonderful book titled “Ignition!”. Overall, ammonia is the best. One last thing: phosphine would be an horrific choice: far too poisonous. $\endgroup$
    – Ed V
    Feb 16, 2020 at 14:11
  • $\begingroup$ I forgot all about hydrogen sulfide! It is poisonous, smells like rotten eggs (because it is the main smell of actual rotten eggs), and it burns in air. Hydrogen selenide (supposedly smells like rotten onions) and hydrogen telluride (supposedly smells like rotten horseradish) are no-go. Interesting question, by the way. $\endgroup$
    – Ed V
    Feb 16, 2020 at 15:51

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Interesting question. These are my candidates, roughly in order from most practical to least practical. Some of these are poisonous, smell very bad, or are just plain undesirable. Environmental issues are not considered herein, but certainly would be in a real world potential application. For details on the chemical substances, see their wiki entries.

  1. As per my first comment and one of the other answers, ammonia, $\ce{NH3}$, is a possibility. It burns in air, is easily liquified for transfort, and is produced in immense quanties already. It has many industrial uses and is not particularly exotic. But is is poisonous and must be handled with respect.

  2. Nitrous oxide, $\ce{N2O}$, decomposes exothermically: this can be initiated with a catalyst and then thermal decomposition takes over. It can be used as a monopropellant and as an oxidizing agent. As 'laughing gas', it has substance abuse issues and does not support respiration. But it is produced in large quantities, is easily liquified for transport and it can be used as the oxidizer in the compustion of, e.g., ammonia.

  3. Hydrazine, $\ce{N2H4}$, has used as a fuel in some rocket engine applications. Hydrazine derivatives such as unsymmetrical dimethyl hydrazine (UDMH) give better performance, but contain carbon. However, maybe amino-hydrazine or hydroxy-hydrazine, assuming they exist, would be viable possibilities. Hydrazine is very poisonous and nasty stuff to deal with. Derivatives probably likewise.

  4. Hydrogen sulfide, $\ce{H2S}$, burns in air, producing water and sulfur dioxide, $\ce{SO2}$. The latter is produced in large quantities when sulfur is burned in the course of producing sulfuric acid, $\ce{H2SO4}$. So the $\ce{SO2}$ product of combustion of $\ce{H2S}$ would have potential commercial value. The downsides are that $\ce{H2S}$ is poisonous and is the main rotten egg smell in actual rotten eggs.

I will add to the list if I think of more.

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  • $\begingroup$ Hydrazine is a liquid, but it was too interesting to omit. $\endgroup$
    – Ed V
    Feb 16, 2020 at 20:48
  • $\begingroup$ There are many more, so many the q. is too broad. $\endgroup$
    – Mithoron
    Feb 17, 2020 at 1:59
  • $\begingroup$ @Mithoron No argument from me! But the OP just wanted a few hypotheticals and I only consider ammonia and nitrous oxide to be even notionally practical. Basically just because they are already made in large quaantities. $\endgroup$
    – Ed V
    Feb 17, 2020 at 2:05
  • $\begingroup$ @Mithoron I see your point - but it could be an interesting answer in the pattern of: There are the obvious candidates a, b and c. There are more candidates in these classes of substances: d based substances, e based substances (and others). $\endgroup$ Feb 26, 2020 at 0:55
  • $\begingroup$ @VolkerSiegel Well, these are mostly hydrides, but lots of them, and well, in most cases it would be unfeasible to use them, or just dumb, or borderline crazy ;) $\endgroup$
    – Mithoron
    Feb 26, 2020 at 1:50
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Yes, ammonia has been cited.

Per a source, 'Ammonia as a Hydrogen Source for Fuel Cells: A Review', to quote:

Like hydrogen, ammonia is carbon free and can be produced from any energy resource. However there are also some significant advantages in terms of storage and transport.

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Boranes like $B_2H_6$ or $B_6H_{10}$ are also a possibility. Probably too expensive !

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    $\begingroup$ It's interesting that among boranes you picked two of the worst possible candidates ($\ce{B2H6}$ instantly hydrolyses and is prone to self-ignition, and $\ce{B6H10}$ decomposes at the room temperature) and didn't mention pentaborane $\ce{B5H9}$, which was actually proposed and briefly used for this very purpose, the energy storage and transport. Plus, the answer might benefit from citing a patent or a literature source as to what the outcome in terms of energy is and what the hazards are. $\endgroup$
    – andselisk
    Feb 16, 2020 at 11:15

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