The race is truly on to find an economic process for producing solar fuels. Chemical fuels produced using solar energy would be the solution to several problems. However efficient silicon and other solar cells and other renewable sources of electricity might become in the future, the world cannot run on electricity alone. Forms of storable energy are needed, not to mention chemical feedstocks for our materials industries. Solar fuels would be able to use the existing infrastructure of petrochemicals plants, pipelines and filling stations. The route is well understood: the processes are simply not yet cost-effective.
Natural photosynthesis is the inspiration but solar fuels will not be produced by imitating it in detail. Natural photosynthesis has two stages: water splitting – producing hydrogen and oxygen – and carbon dioxide reduction to yield hydrocarbons and hence the panoply of organics. For now the emphasis is on water splitting: “fuel from air and water” is already a commercial operation where cheap electricity from hydrothermal sources is used for water splitting and carbon dioxide is then reduced to organics by the hydrogen. But to be able to produce hydrogen from sunlight would be a game changer for the whole world.
Now Michael Grätzel’s team at Lausanne (of fuel-cell fame) have coupled a perovksite solar cell to a cheap water-splitting catalyst to produce solar hydrogen with a 12.3% solar energy:hydrogen efficiency (natural photosynthesis is less than 1% efficient).
Tantalisingly, the new system so far meets only three of the requirements for a commercial process: efficient, cost-effective, scalable, and stable through many cycles. The perovskite solar cells fall at the last hurdle and urgent work is now being done to address this.
Science, 26 September 2014, pp. 1566-7; 1593-6.
Natural photosynthesis is the inspiration but solar fuels will not be produced by imitating it in detail. Natural photosynthesis has two stages: water splitting – producing hydrogen and oxygen – and carbon dioxide reduction to yield hydrocarbons and hence the panoply of organics. For now the emphasis is on water splitting: “fuel from air and water” is already a commercial operation where cheap electricity from hydrothermal sources is used for water splitting and carbon dioxide is then reduced to organics by the hydrogen. But to be able to produce hydrogen from sunlight would be a game changer for the whole world.
Now Michael Grätzel’s team at Lausanne (of fuel-cell fame) have coupled a perovksite solar cell to a cheap water-splitting catalyst to produce solar hydrogen with a 12.3% solar energy:hydrogen efficiency (natural photosynthesis is less than 1% efficient).
Tantalisingly, the new system so far meets only three of the requirements for a commercial process: efficient, cost-effective, scalable, and stable through many cycles. The perovskite solar cells fall at the last hurdle and urgent work is now being done to address this.
Science, 26 September 2014, pp. 1566-7; 1593-6.
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