The most efficient way to turn sunlight into energy has existed for around 400m years: photosynthesis. Scientists have been attempting to replicate this in artificial leaves for some time and have now taken a step forward by replacing expensive materials with cheaper ones.

This is significant, because while artificial leaves could be the fuel cells of the future, production costs remain a major issue. One of the biggest obstacles to artificial photosynthesis has been that scientists could only replicate it with a costly platinum catalyst. Now Danial Norcera at Massachusetts Institute of Technology (MIT) says his team has found a way to replace it with a cheap nickel-molybdenum-zinc compound. This puts him one step closer to his goal of finding an inexpensive, portable source of renewable energy for developing countries.

Artificial leaves – recently profiled by the New Yorker – resemble a thin playing card, described by MIT as a “silicon solar cell with different catalytic materials bonded onto its two sides”. Covered with water and placed in sunlight, it splits hydrogen and water, mimicking photosynthesis.

In a real leaf, the hydrogen is then combined with CO₂ from the atmosphere to make sugars, cell walls and other organic matter. In the artificial version, scientists use the hydrogen in fuel cells to make electricity or else combine it with CO₂ to make fuels such as methanol. This could be used in car engines, much as ethanol biofuels are used today and would provide a carbon-neutral source of power.

“I’ve got to say that the Norcera 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,” said Jim Barber, a biologist at Imperial College London.

Barber is part of another team researching artificial photosynthesis. His project uses iron oxide, or rust, as a cheap material to absorb light and serve as a semi-conductor. “The sun is the only energy source available to us of sufficient magnitude to satisfy our needs. That’s why it’s so important to continue to develop the research and development. The Nocera work is a giant leap forward towards this goal of capturing sunlight and storing it as a fuel,” Barber explained.

Artificial leaves would also fill some of the gaps left by other renewable energy technology. They could be used in arid regions where hydropower is unfeasible, they take up less space than solar panels and don’t require a battery to store energy.

According to Barber, if artificial photosynthesis systems could use around 10% of the sunlight falling on them, they would only need to cover 0.16% of the Earth’s surface to satisfy a global energy consumption rate of 20 terawatts, the amount it is predicted that the world will need in 2030.

Norcera may be one of the first researchers to commercialise his technology: Wired reported that he signed a deal with the Tata group to build a small power generator the size of a refrigerator.