Researchers at the US Department of Energy’s Pacific Northwest National Laboratory (PNNL) have found a way to release hydrogen from a solid compound almost 100 times faster than was previously possible.
The compound in question, ammonia borane, can release hydrogen at temperatures below 80 degrees Celsius, but the rate of release is extremely slow. In the nanophase, however, the hydrogen comes off very fast – approximately 100 times faster compared to conventional bulk ammonia borane.
So the trick the researchers employed was to transform the ammonia borane into a nanomaterial.
To do so, the scientists first dissolved the solid compound in a solvent and then added the solution to a nanoscale mesoporous silica material, which acted as a ‘scaffolding’ material. The capillary action of the porous material pulled the ammonia borane into the pores of the support. When the solvent was removed, nanosized pores – about 6.5 nanometres in diameter – filled with ammonia borane were left.
The resulting compound released hydrogen 100 times faster than was previously possible.
Based on computational thermodynamic analysis, researchers believe the process may eventually be designed to be reversible, which would allow the storage material to be regenerated and provide a sustainable hydrogen storage compound with a longer lifetime.
A patent is pending on the process.