Hydrogen - fuel of the future?

As CO2 targets demand alternatives to non-sustainable fossil fuels, and fears over the safety of nuclear power grow following the Fukishima incident in Japan, the search for a safe, sustainable energy source to meet the demands of a power-hungry planet, grows ever more urgent. Could hydrogen be the holy grail?.

When it comes to a safe, clean, sustainable energy source, hydrogen ticks a lot of boxes. It is colourless, odourless emission free, can be used for a variety of energy needs and, being a constituent of water and other common compounds, is the most abundant element on Earth. The challenge is to convert the hydrogen from water efficiently, affordably and sustainably, and be able to store it at sufficiently high density.

Less sustainable methods of ‘water splitting’ as the process is known, use fossil fuels to achieve this reaction, via steam. Indeed, around 95 per cent of hydrogen production in the US is still done by ‘steam reforming’ another natural gas, methane. But the very use of fossil fuels to do so, of course, negates much of the environmental benefit. Later attempts to split water have turned to photoelectrolysis – converting light into an electric current and conducting the current, via an electrode, to attract the hydrogen (H2) away from the oxygen (O).

MATCON (MATerials and interfaces for energy CONversion and storage), the training and research network coordinated by Professor Larsson, is taking such photoelectric techniques one stage further – using nano-sized particles for greater efficiency and stability. “Water splitting is not a new area of research but the materials and methods we are researching certainly are,” says Professor Larsson, of the four-year project that began in 2009. “Our purpose is to find new materials or combinations of materials that overcome existing problems of stability. So the project puts considerable emphasis on the development of such materials for electrodes, substrates and interfaces.”

The network operates across six EU countries – Sweden, the Czech Republic, Germany, Austria, Belgium and the UK, blending expertise from nine partners in chemistry, physics and engineering. “The urgency for renewable energy has created a real demand for well-educated young scientists knowledgeable in materials science,” says Professor Larsson. “MATCON provides that essential learning environment around state-of the art materials, within a live research project, while the significance of the research topic provides the purpose – and of course attracts the funding. So the bulk of the research is carried out by PhD and post-graduate students, supervised by myself and other senior research colleagues.”

The advanced techniques are a natural progression of the research that Professor Larsson began in 1989, when she first started growing synthetic diamonds. “We are currently researching two main water splitting processes. The first is a photoelectric process, where we grow a synthetic nano-crystalline diamond and then use a suitable metal, such as platinum, gold or titanium, to act as a catalyst for the reaction,” she explains. “The second is a biomimetic approach. It’s a similar concept, but we harness the natural energy of photosynthesis by using an artificial “plant” with the diamond instead, and taylor-make the interface between the plant and the diamond (e.g. by inserting a layer of graphene) to improve the electron transfer process.”

The concept is intriguing, but the challenge facing the project is to improve the efficiency of the energy conversion, along with the stability of the reaction, says Professor Larsson. “One of the key parts of our research is to find a way to control the growth of the synthetic diamond so that it consistently produces crystals of nano-particle size,” she says. If the particles grow too large, the reaction cannot work efficiently.

We also need to learn how to control the catalytic reaction, to create stability. The metal and diamond work best when they are fused together to make an efficient composite material for the chemical reaction. But getting them to stay together in this way is very difficult so we’re still learning how to do that. And for the biomimetic process, we need to find which interfacial structure acts as the most efficient electron bridge between diamond and the chromophore.

The need for costly precious metals for the photoelectric process would seem a significant obstacle to creating an affordable power source too, but Professor Larsson says this is not seen as a long-term requirement. “At the moment we need to use metal as part of the process, but we think the reaction can actually be done using just the diamond – we just have to work out how,” she says. “We would hope to reach that stage within six or seven years from now.”

But do modern extraction methods for fossil fuels, such as hydraulic fracturing (‘fracking’) of gas seams in deep rock beds, mean there is now less urgency to find sustainable methods of energy conversion? “Any fossil fuel, by its very nature, will run out, and also contributes hugely to CO2 output at a time we are urgently needing to reduce our emissions,” says Professor Larsson.

“So fossil fuels are not the answer – they’re actually part of the problem. The need for our kind of research, to develop a sustainable energy source, is more urgent than ever.”

With just another 18 months or so of the project to run under its current round of funding, where does Professor Larsson hopes the project will be by then? “Well, we hope we can overcome the challenges that I’ve mentioned and produce hydrogen from both these methods efficiently and in a stable, controlled way. What the planet requires urgently is a renewable energy source that excels in three ways: pricing, efficiency and environmental control.

“The hope for the future, of course is that our techniques for water splitting could ultimately be made so efficient that they could provide a viable alternative to fossil fuels and nuclear power. But that goal is not really part of our research – we don’t want to get ahead of ourselves. For the time being we’re just trying to find a way to make the techniques work effectively– and make a significant contribution to the training and development of the next generation of materials scientists.”

Click here for the project website.

Published: Tuesday, 24th January 2012