The development of a sustainable energy economy, based not on limited fossil fuels, but on renewable, carbon-neutral energy is a necessary and urgent task. Hydrogen (H2) is a leading candidate for the storage and transportation of energy provided it can be efficiently produced from renewable energy sources and effectively stored in a safe and concentrated manner. Solar energy, the largest and most promising renewable source available, has the potential to provide sufficient power for carbon neutral H2 production via water hydrolysis on the scale required. However, solar electricity for electrolysis of water generated by state-of-the-art photovoltaics (PV) or concentrating thermal power (CSP) still remains too expensive to compete with other forms of electricity generation. Moreover, sustainable and efficient H2 production alone is not enough to realize a carbon-neutral energy economy - the safe and efficient storage and transportation of H2 also remains a critical issue for the transition towards a hydrogen-based energy supply system.