Understanding the detection mechanisms and ability of molecular hydrogen on three-dimensional bicontinuous nanoporous reduced graphene oxide

Abstract

Environmental safety has become increasingly important with respect to hydrogen use in society. Monitoring techniques for explosive gaseous hydrogen are essential to ensure safety in sustainable hydrogen utilization. Here, we reveal molecular hydrogen detection mechanisms with monolithic three-dimensional nanoporous reduced graphene oxide under gaseous hydrogen flow and at roomtemperature.Nanoporous reduced graphene oxide significantly increasedmolecular hydrogen physisorption without the need to employ catalytic metals or heating. This can be explained by the significantly increasedsurface area in comparison to two-dimensional graphene sheets andconventional reduced graphene oxide flakes. Using this large surface area,molecular hydrogen adsorption behaviors were accurately observed. In particular, we found that the electrical resistance firstly decreased and then gradually increased with higher gaseous hydrogen concentrations. The resistance decrease was due to charge transfer from the molecular hydrogen to the reduced graphene oxide at adsorbed molecular hydrogen concentrations lower than 2.8 ppm; conversely, the resistance increase was a result of Coulomb scattering effects at adsorbed molecular hydrogen concentrations exceeding 5.0 ppm, as supported by density functional theory. These findings not only provide the detailed adsorption mechanisms of molecular hydrogen, but also advance the development of catalyst-free non-heated physisorption-type molecular detection devices.