Hydrogen gas

Hydrogen gas (H2) is a fuel that when burned, produces no pollution and no carbon emissions - only water vapor (H2O). Just one problem: There are no natural resources of hydrogen gas.

To make hydrogen gas, you need to use some other energy source.

Production

Electrolysis

Electricity can turn water (H2O) into hydrogen gas (H2) and oxygen gas (O2).

The electricity could come from renewable sources such as solar, wind, or hydro.

Research needed for this page

Can electrolysis be done efficiently on a medium scale, for example using the energy from a rooftop of solar panels?

Are rare minerals needed to make efficient electrolysis machines? If so, which minerals and how much of them; what are the different options?

From fossil fuels

Currently most hydrogen is produced from natural gas via steam reforming, but this emits just as much CO2 as burning the natural gas itself.

There's another (similar) process called methane cracking which takes in natural gas, and produces hydrogen gas + solid carbon (not CO2) which could be buried in the ground or used for something else. The main problem, currently, is that it takes more energy than you ultimately get from burning the hydrogen gas. In theory, it doesn't have to. [''']Chemistry equations:
CH4 -> C + 2 H2 (endothermic: 74.850 kJ/mol)
2 H2 + O2 -> 2 H2O (exothermic: 285.820 kJ/mol)

Uses

Most hydrogen gas today is used in making fertilizer.

But in the future it could also be used for:

The general idea would be to use surplus electricity to generate hydrogen gas, and then use it as a fuel later.