Experts: Greta R. Patzke (University of Zurich), Kevin Sivula (EPFL)
Artificial photosynthesis is a way of producing hydrogen or synthetic hydrocarbons with sunlight. Although the procedures used for this are only starting to be developed today and are therefore far from economically viable as yet, it can be assumed that they will one day make an important contribution to a sustainable energy supply.
Picture: Getty Images
Artificial photosynthesis refers to a number of different procedures that use sunlight to drive chemical processes, thus mimicking natural photosynthesis, the process by which plants store energy or produce biomass. Both artificial and natural photosynthesis use solar energy to split water molecules into hydrogen and oxygen, then convert these into hydrocarbons by introducing carbon dioxide (CO2) from the atmosphere or from industrial exhaust gases. Both hydrogen and hydrocarbons can be used as carbon-neutral energy carriers, or for other industrial processes.
Research and development into water splitting mainly pursues two directions: The simplest option combines existing technologies from photovoltaics and electrolysis in a two-step procedure –generating solar power, then using this in an electrolyser to split water. This technology is already application-ready, but there is room for research and improvement, especially in terms of processes and materials, e.g. regarding cheaper catalysts, bubble formation during electrolysis, electrode service life and increased efficiency. The second option being pursued is the direct photo(electro)catalytic use of solar energy for single-step water splitting. This technology is still at an early developmental stage, involving individual prototypes. With direct one-step artificial photosynthesis, the aim is to achieve higher efficiency in the future than the current two-step procedures.
Hydrogen produced by artificial photosynthesis can be stored, or used in fuel cells, gas turbines and the like, to generate electrical current or to run hydrogen-powered vehicles. The hydrogen can also be used as a starting material for industrial production of commodity chemicals (e.g. ammonia). With the aid of established technologies (e.g. the water-gas shift reaction and the Fischer-Tropsch process), carbon-neutral combustibles and fuels can be produced using hydrogen and CO2 from the atmosphere or from industrial exhaust gases. In the longer term, artificial photosynthesis can thus help to establish hydrogen and other synthetic energy carriers as an important basis for a sustainable energy economy and to decarbonise various applications in transport and industry.
Switzerland is not very well positioned to produce its own hydrogen or other solar combustibles and fuels, as the hours of sunshine here are hardly sufficient. However, other power-to-X solutions are promising: wind-power electrolysis, for instance. At the same time, Switzerland has long been a leader in research and development involving solar energy conversion. Given the importance of artificial photosynthesis technology, there is a clear opportunity for state funding agencies to strongly support basic research and development of these technologies, so that the resulting intellectual property remains in Switzerland.
Systems that combine photovoltaic cells with an electrolyser are already in operation. However, the hydrogen produced in this way is generally still more expensive than that from competing methods of hydrogen production, such as steam-reforming of natural gas. For this reason, the technology has not yet caught on. Accordingly, two-step artificial photosynthesis for the production of hydrogen is not competitive. The price of producing hydrogen using solar and/or wind energy is expected to drop significantly though. Nevertheless, there is still a need for research and development to lower the cost of these technologies.
By virtue of their integrated nature, different, one-step approaches to artificial photosynthesis (e.g. photoelectrochemical or photocatalytic systems) are likely to produce solar fuels more efficiently and in a more economically competitive manner, but the technology behind these methods is less mature and currently still at the research stage.
All artificial photosynthesis procedures require only solar energy, water and CO2 as feedstock. This means that unlike other biofuel production processes, there is no conflict of goals with food production or other biomass uses.
Research efforts at all levels, from gaining fundamental knowledge about photocatalysis to conducting pilot demonstrations of technologies, should be supported. The benefits for the Swiss economy are currently still in the early stages, but further development of the underlying technologies offers great opportunities for Switzerland to play a pioneering role in establishing new energy technologies. Due to the limited hours of sunshine in Switzerland, the primary course of action will be to develop and demonstrate the feasibility of artificial photosynthesis processes in pilot systems within Switzerland with the aim of subsequently implementing them on a commercial scale at more suitable locations in other parts of the world. This would provide a good basis for future Swiss technology exports.
