Taking a leaf from nature: the quest for a new cheap energy source

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The scientific pursuit of a way to artificially replicate photosynthesis, and thus develop a cheap and versatile source of carbon-neutral renewable energy, has been gaining serious momentum over the last year or so, thanks in no small part to the efforts of MIT energy and chemistry professor Daniel Nocera. And this week, the Director of MIT’s Solar Revolutions Project (and Sun Catalytix founder) and his team appear to have achieved a new milestone.

ScienceDaily reports that a detailed description of the development of the first practical artificial leaf, published in the ACS journal Accounts of Chemical Research, has noted that unlike earlier devices, which used expensive ingredients, the new model is made from inexpensive materials and employs low-cost engineering and manufacturing processes.

The MIT-developed artificial leaf, which look less like a leaf and more like a playing card, is better described as an advanced solar cell. Or technically speaking, silicon solar cells with different catalytic materials bonded onto either side. When covered with water and placed in sunlight, they split hydrogen and water, mimicking photosynthesis – but in this case, the process results in the release of bubbles of hydrogen that can be used in fuel cells to make electricity.

Last year, Nocera told the National Meeting of the American Chemical Society in California that his team’s  artificial leaf could operate continuously for at least 45 hours without a drop in activity and was much as 10 times more efficient at carrying out photosynthesis than a regular leaf. As ScienceDaily says, such characteristics make these self-contained units very attractive for generating power in far-flung places and the developing world, but thus far their production has relied on rare and expensive metals like platinum, and complex manufacturing processes that make them cost-prohibitive.

To address this problem, Nocera has replaced the platinum catalyst with a less-expensive nickel-molybdenum-zinc compound, while on the other side of the leaf, a cobalt film generates oxygen gas. Nocera notes that all of these materials are abundantly available, unlike platinum, or the noble metal oxides and the semiconducting materials others have used.

“The Nocera work is a giant leap forward towards this goal of capturing sunlight and storing it as a fuel,” Jim Barber, a biologist at Imperial College London, tells The Guardian. Barber, who is part of a team researching another method of artificial photosynthesis using iron oxide (rust), describes the sun as the only energy source “of sufficient magnitude” to satisfy the world’s growing needs. “That’s why it’s so important to continue to develop the research and development,” Barber says. “I’ve got to say that the Nocera system is very good – it’s probably at the moment the best in the world, but there are other alternative approaches and many places are working on it.”

Barber also says that artificial photosynthesis systems using around 10 per cent of the sunlight falling on them would only need to cover 0.16 per cent of the Earth’s surface to satisfy a global energy consumption rate of 20 terawatts, the amount it has been predicted that the world will need in 2030.

Which brings us back to Nocera’s ultimate research target: to create a readily portable source of clean, renewable energy to meet the needs of “the 6 billion nonlegacy users” that are driving the enormous increase in global energy demand by midcentury. “Our goal is to make each home its own power station,” Nocera said last year. “One can envision villages in India and Africa not long from now purchasing an affordable basic power system based on this technology.”  


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