Hydrogen storage receives the worldwide attention due to its importance in sustainable energy and the solution of greenhouse effect.Adsorption provides an efficient way to compress gases and,therefore, has been applied to the development of hydrogen storage technology.However,hydrogen is a super- critical gas at the temperature of engineering interest and follows a different adsorption mechanism compared to the sub-critical gases.The present work shows why only monolayer coverage mechanism functions at above-critical temperatures and what consequences will result in the application study. Although there are pros and cons to this point of view,understanding the adsorption mechanism is,in- deed,essential for the research of hydrogen storage method since it claims that any storage material based on adsorption will not satisfy the practical need of on board storage no matter how novel the material is.
Storing natural gas in wet active carbon is a recently proposed method. The research progress shows that this method considerably decreases the storage pressure while maintaining the storage capacity equal to or even higher than compressed natural gas （CNG）. There is no requirement of pre-sifting any component out of natural gas for the storage, and the thermal effect on fast charging/discharging has almost no effect on the storage capacity. The charging and discharging processes are reversible and show good dynamic behavior. Although the storage temperature is a little lower than the ambient, the new method seems technically and costly more competitive than the available methods.
