Question: why are your artifical leaves better than electrolysis of water to produce hydrogen?

Stuart Archer answered on 25 Jun 2013:

That’s a really good question! The problem with water electrolysis is that it’s a pretty inefficient process in terms of the amount of hydrogen generated compared to the amount of electricity you need to put in, as you need to overcome a large ‘activation energy barrier’ to electrolyse pure water. You can overcome this by adding an ‘electrolyte’ (an electrically-conductive chemical) to the water – typically this is sulfuric acid! I’m sure you can appreciate that there are hazards associated with this. In addition, the materials required to construct the cell include things like pure platinum metal – which is very expensive! You ALSO need a source of electricity – currently this is mainly supplied by fossil fuels, which only generate electricity at about 40% efficiency. Overall this means that from fuel to hydrogen you max out at around 30% efficiency.

In an ideal world, with an artificial leaf all you would need to make it work is pure water and sunlight. Whilst we’re unlikely to exceed 20% efficiency, this is less important as the energy source you are using (the Sun) is free! We’re a long way from making these things commercially yet – at least 10 years – but there’s definitely potential in them if we can over come some of the challenges!