Current methods for production

The current commercial process for producing hydrogen is steam reforming of natural gas. Hydrogen can also be produced from coal using gasification technology. Both methods have as disadvantages that they result in CO2 emission (even if CO2 could be sequestered, the safety of sequestration techniques is presently under discussion), that the availability of natural gas and coal is limited, and a disadvantage of natural gas is that most of it is present in non-EU, sometimes unstable countries, with consequences for energy security [6]. Other methods of producing hydrogen use nuclear energy, electricity from solar cells or from wind energy, biomass (which cannot be grown in sufficient quantities to fulfill world energy needs), and photobiological and photoelectrochemical processes [6]. Photoelectrochemical hydrogen production is mentioned in both a recent energy technology analysis of the International Energy Agency (IEA) [6] and in a recent report of the National Research Council and the National Academy of Engineering of the US (NRC/NAE report) [5] as an important research area where the kind of technological and conceptual breakthroughs required for the hydrogen economy are possible, and the network will focus its research on production of hydrogen exclusively on this production technique.


Current methods for storage

Hydrogen storage technologies are discussed in a recent review paper co-authored by one of the applicants [7]. Storage in gaseous form requires too much volume in automobiles, and one third of the energy content of H2 is needed to liquify hydrogen. Adsorption on carbon nano-tubes only leads to reasonable weight percentages of adsorbed hydrogen at liquid nitrogen temperatures. Conventional metal hydrides either exhibit a too low weight percentage (PdH0.6, LaNi5H6), or thermodynamics dictates that they release hydrogen at too high temperatures (MgH2, 300°C). Very recently proposed systems all exhibit particular problems (promoted clathrate hydrates release H2 at a too low temperature [8], metal organic frameworks still show a too low weightpercentage of H2 [9], organometallic buckyballs may work well if scandium is used [10], which however is too expensive, titanium-decorated carbon nanotubes bind hydrogen too strongly [11]). The network will focus its research on the three classes of systems it considers most promising, i.e., alanates, borohydrides, and a new material in which H2 is stored as ammonia in a stable and environmentally friendly co-ordination compound. Complex metal hydrides are mentioned in the IEA [6] and NRC/NAE [5] reports as a type of material for which the kind of technological and conceptual breakthroughs that are needed for the introduction of the hydrogen economy are possible.


What is needed

To realise the hydrogen economy, conceptual and technological breakthroughs are needed in the areas of production of renewable hydrogen and hydrogen storage. Production methods based on solar energy ideally convert solar energy to chemical energy in hydrogen with an efficiency of at least 10%, and are based on cheap materials. According to the IEA [12], storage compounds should exhibit a 5 wt% content of H2;. In addition the compound should take little volume, the adsorption and desorption of H2 should be reversible and occur close to the PEM fuel cell operating temperatures (~ 80 °C) and ambient pressures, and the storage medium should be cheap and not exhibit undesirable properties [7, 13].

11/11/2010