The growth of the so-called “hydrogen economy” is crucial to achieving net-zero carbon emissions targets across the world. Under the hydrogen economy vision, the world will reduce its dependence on fossil fuels by using hydrogen as a fuel instead.
Hydrogen is one of the most promising alternative fuels because it is abundant, renewable, and clean: the only biproduct of burning hydrogen is water vapour. Hydrogen gas can also be transported through pipelines in much the same way that natural gas is currently, making it compatible with existing systems.
New innovations using graphene are helping support the hydrogen economy, both in a practical sense (moving and storing hydrogen) and a chemical sense (generating hydrogen to move and store!).
Graphene as a hydrogen barrier
An inherent property of hydrogen presents a unique challenge for its transportation and storage, which threatens its scalability to meet net-zero targets.
Molecular hydrogen, H2, is the smallest molecule in existence. It has a diameter ⅔ that of methane, the smallest constituent of natural gas. As a result, hydrogen is susceptible to leaking through pipes and containers. In fact, hydrogen is so small that it can permeate through the walls of conventional vessels, which means that it can leak even if the container doesn’t have any defects.
Leakage impacts the economic viability of hydrogen as an alternative fuel. Releasing hydrogen gas into the atmosphere can also contribute to the global warming effect, defeating the purpose of using hydrogen as a greener source of energy.
Graphene has exciting potential for reducing hydrogen leakage, given that pristine graphene is nearly completely impermeable to gases. Graphene is also highly versatile as an additive and can be formulated into polymer and metal composites to enhance their properties, even at low loadings. A number of innovators have therefore looked to graphene as a potential solution to the leakage problem.
For example, Graphmatech have collaborated with Steelhead Composites to use graphene as an additive in liners covering the inside or outside surfaces of type IV pressure vessels. Here, flakes of graphene in the liner material make it more difficult for hydrogen molecules to escape through the liner, which reduces leakage.
Taking a slightly different approach, Viritech and Haydale have also partnered together to develop linerless type V pressure vessels, where graphene is incorporated into the metal alloy of the vessel itself.
Producing hydrogen through graphene
Hydrogen is the most abundant element on earth. However, isolating hydrogen at scale in a form that can be used as a fuel is challenging and not always environmentally friendly. Currently, the leading method for producing hydrogen fuel is electrolysis, which uses electrical current to split hydrogen from water. The power grid usually provides this electricity, some of which is produced by burning fossil fuels.
Addressing this ‘flaw’ in the green credentials of hydrogen as a fuel, Levidian have developed a device called LOOPTM, which ionises methane into a plasma and then converts it into graphene and hydrogen. As a result, not only does LOOP produce “green” graphene by consuming methane – a major contributor to the greenhouse effect – but it also produces hydrogen as an environmentally friendly alternative fuel as a biproduct.
The LOOP technology is well positioned to support the hydrogen economy due to its compatibility with current infrastructure. LOOP is designed to dock seamlessly into existing power generators, gas grids and biogas plants. Importantly, LOOP can also be adjusted to produce either pure hydrogen or a partially decarbonised hydrogen-methane blend. This tuneability enables LOOP to produce a hydrogen fuel which suits the requirements of various existing combustion systems.
Outlook
Demand for hydrogen is set to grow as governments and industries push towards a net-zero future. Graphene can play an important facilitating role, aiding in storage and transportation infrastructure and encouraging a hydrogen synthesis route which generates useful products from an environmentally disfavoured starting material.
