Super fuel ready to supersede oil
A technology that converts sunlight directly into fuel using ‘‘artificial leaves’’ could become a viable alternative to taking oil from the ground, scientists say.
In recent weeks, huge leaps in the technique have led researchers to say there are now no big technical obstacles to its arrival as a new form of renewable energy.
In the same way that plants use sunlight to turn carbon dioxide and water into glucose, the artificial leaves use the Sun’s energy to turn carbon dioxide and water into hydrocarbon fuels similar to those we take from oil.
In a two-stage process, the leaf first splits water into hydrogen and oxygen, and then uses either a biological or chemical process to take carbon dioxide from the atmosphere and combine it with the hydrogen to make a fuel.
The advantage in doing so, compared with conventional solar panels, is that the energy is stored immediately and in a far denser form than a battery can ever achieve. A kilogram of petrol stores 30 times as much energy as a kilogram of battery.
The fuel can also, in theory, be easily converted into a form that can be used in cars.
However, the technology has lagged behind solar panels. Conventional solar panels, known as photovoltaic cells, take sunlight and convert it directly into electricity, with an efficiency rate of about 20 per cent.
Now a team at Harvard University has created a leaf that makes fuel directly, using bacteria, at a greater efficiency than has been achieved before – and at 10 times the efficiency of natural leaves, although still less than solar panels.
Yesterday a team at the University of Illinois announced they had improved the efficiency of a method of making fuel using chemical methods.
‘‘We have beaten photosynthesis by a factor of 10,’’ said Daniel Nocera, from Harvard, of his paper, published in the journal Science. While plants convert only about 1 per cent of sunlight into fuel, his latest iteration of an artificial leaf converts 10 per cent.
‘‘I can definitely see a path forward now,’’ he said. ‘‘There’s still a lot to be done, and you can always keep improving. But we can be way better than nature in taking sunlight and making fuels. I find that massively encouraging.’’
Amin Salehi, from the University of Illinois, had been working on an alternative approach. Using sunlight to split water into hydrogen and oxygen, his team has developed a catalyst called nanoflake tungsten diselenide that simultaneously converts carbon dioxide into carbon monoxide in the leaf, at greatly improved efficiency compared with conventional noble metal catalysts. When combined with the hydrogen, the carbon monoxide produces a fuel called syngas that can then be used as the basis of hydrocarbons.
‘‘The catalyst has 12,000 times