The NanoComposites for Active Gas Encapsulation (nanoCAGE) project will deliver smart composite materials to address the problem of safe and efficient hydrogen storage.

As a future replacement for fossil fuels, hydrogen is a promising low-carbon, renewable energy carrier, but as a low-density gas it is challenging to store on board a vehicle. Nanoporous materials (materials containing holes only a few nanometers in diameter) have been shown to spontaneously adsorb hydrogen so that it can be stored at exceedingly high densities under the right conditions. However, storage of industrially relevant amounts of hydrogen (i.e. at levels approaching US Department of Energy technical targets) via adsorption in porous materials necessitates storage at very high pressures (typically >350 bar) or very low temperatures (e.g. 77 K).

The work described here challenges conventional approaches to the development of porous materials for storage of hydrogen which rely on simple adsorption of gases onto materials surfaces, and instead will change the mechanism by which the hydrogen is stored. These new composites will be based on encapsulating existing nanoporous adsorbents in a continuous matrix of an active material that can control when gases are allowed in or out of the pores of the adsorbent. The novel approach is that the active components will be triggered to undergo a reversible change in structure to induce controlled and reversible pore blocking to either allow or obstruct the movement of gases to or from the pores of the adsorbent, allowing these materials to act as a "nanocage" for gas molecules.

Another key innovation of the nanoCAGE project is the introduction of control over the trapping and release mechanisms using changes in external conditions such as light, heat or application of a magnetic field to change the structure of the active phase.

This approach, building upon the PI's expertise in hydrogen densification in nanoporous materials, could increase the amount of hydrogen stored in these materials at room temperature by ten times, making economical storage of hydrogen possible and providing a gateway to use of hydrogen for sustainable energy applications. This will accelerate the adoption of non-polluting hydrogen fuel cell vehicles and will lead to benefits to the UK in terms of improved air quality, reduced carbon emissions and decreased reliance on imports of fossil fuels.

These composite materials could furthermore find application in many other fields of research (for example in carbon dioxide capture, controllable drug delivery and smart packaging) and will allow the PI to develop an exciting new research area in active gas trapping composites.

Potential Impact:
Provision of higher capacity and more robust new materials that could be used to safely and efficiently store hydrogen would facilitate the widespread adoption of hydrogen as a sustainable, non-polluting alternative to fossil fuel-based energy systems. The development of such materials would have demonstrable positive impacts on the economy, through the creation of new jobs and industries based on the use of hydrogen as a fuel source, reducing reliance on foreign oil and gas and providing a method of storing surplus renewably-generated energy as hydrogen.

There will also be positive impacts on the environment, through elimination of carbon dioxide and pollutant emissions resulting from combustion of fossil fuels. Vehicular carbon emissions, air pollution and the negative effects on health and the environment are a growing concern with the transportation sector accounting for 40% of total energy consumption in the UK in 2015 [2]. High-performance energy storage materials are expected to make a significant environmental impact, as affordable and efficient energy storage is one of the current barriers precluding further growth of the renewable energy sector. Growing the share of renewable energies in the energy mix will help the UK reach its legislated decarbonisation targets, contributing to a cleaner and more sustainable energy system.

Finally, there will be many positive impacts on public well-being, through improved air quality, lower domestic fuel prices and new products such as quieter, non-polluting fuel cell vehicles. In addition, replacement of fossil fuels with hydrogen (which can be generated from water using surplus renewable energy) will enable the UK to generate a greater proportion of its own energy domestically, decreasing reliance on imported fossil fuels, which may result in lower energy costs, reductions in energy poverty and increased energy security for the UK.

Beyond the UK this research could enable use of sustainable energy storage worldwide. This could remove barriers to industrial development and economic growth, result in lower carbon dioxide emissions and reduced climate change as well as making provision of sustainable energy more equitable and widely available, addressing a range of urgent global issues and resulting in positive impacts on a global scale.

[1] Energy Consumption in the UK 2016, Department for Business, Energy & Industrial Strategy (https://www.gov.uk/government/statistics/energy-consumption-in-the-uk, accessed 1/5/17);