Artificial Photosynthesis

The imitation of the mechanism used by plants to produce the high-energy compound glucose through the combination of water and carbon dioxide, using the energy of photons from sunlight. In green energy systems, this technology would provide a fossil fuel free energy storage system, such as a hydrogen-based fuel. In combination with carbon dioxide extraction from the atmosphere, it could offer a carbon negative energy source.

The usual way to produce green hydrogen from sunlight is through photovoltaics generating electricity, which is then used in a electrolytic cell to produce hydrogen from water. This method does not compete economically with hydrogen production from fossil fuels, such as natural gas.

Photocatalytic water splitting may offer a more efficient method of producing hydrogen. It uses photosemiconductor catalysts to convert sunlight into hydrogen more directly than through electrolysis. Two systems may be used:

1. A homogeneous system in which the catalysts are not compartmentalised, and all components are present in the one cell. Hydrogen and oxygen are produced together, requiring gas separation afterwards.

2. A heterogeneous system with two separate electrodes for separate hydrogen and oxygen production.

Photosynthetic micro-organisms, such as microalgae and cyanobacteria, may be used in solar fuel production. Algae biofuels already produce butanol (C4H9OH) and methanol (CH3OH). Synthetic biology attempts to produce synthetic organisms for biofuel production.

Microalgae: responsible for half of the atmosphere’s oxygen. They grow photoautotrophically, feeding on atmospheric carbon dioxide.