Exploring the impact of doping and co-doping with B and N on the properties of graphene oxide and its photocatalytic generation of hydrogen

The photocatalytic production of hydrogen was studied in graphene oxide materials doped with nitrogen or/and boron by hydrothermal treatments. Characterization of the materials was carried out by XRD, FTIR, XPS, Raman, UV–Vis, and photoluminescence spectroscopies, FESEM and TEM. The study of hydrogen evolution in the water splitting reaction was done using UV light as source of irradiation and methanol as hole scavenger. Boron-doped graphene oxide with the highest bulk electrical resistance exhibited the highest photocatalytic hydrogen generation, due to interstitial positioning of boron in the graphene lattice, which improved the light absorption coefficient, formation of inter-gap states and reduced charge recombination. This phenomenon is hypothesized for the first time as “decentralized reaction clusters”, which spread across the graphene lattice and produce hydrogen independently. Nitrogen-doped graphene oxide showed high electrical conductivity due to a significant removal of oxygen functional groups, and improved carrier density. Partially reduced nitrogen and boron co-doped graphene oxide showed the highest electrical conductivity, due to the presence of more electron-donating nitrogen configurations, such as pyrrolic N and pyridinic N. Nitrogen and boron co-doping of graphene oxide allows to modify the conduction band and valence bands, thus improving the electrical conductivity.