Thermal decomposition of methane

An experiment was done in which concentrated solar energy is used to split methane into hydrogen and carbon black (pdf).

We propose an alternate strategy using highly concentrated
sunlight as the energy source that does not result in an increase of environmental liability.  Indeed, it represents a route for utilizing current natural gas reserves that fixes carbon as well as increasing the energy content of the fuel.

This could be the cheapest way to obtain hydrogen for fuel cells.