Decorating platinum on nitrogen-doped graphene sheets : Control of the platinum particle size distribution for improved photocatalytic H₂ generation

Nitrogen doping of graphene with systematically controlled dopant content and distribution of nitrogen species is demonstrated to improve the size distribution of the deposited platinum (Pt) nanoparticles. While the dopant content can be tuned by varying the urea dosage, the doped nitrogen species (namely pyridinic N, pyrrolic N, and graphitic N) can be controlled through the annealing temperature. Chemically reduced Pt nanoparticles were found to be evenly distributed on the nitrogen-doped graphene sheets (NRGO) with particle size centred at 2.7 nm. In comparison, the decoration of Pt on the non-doped graphene (RGO) yielded a composite material with larger Pt (7.8 nm) and poorer size distribution. The loading of Pt nanoparticles is shown to correlate with the concentration of the nitrogen dopant, in particular that of the graphitic N species. Owing to the smaller and better distributed Pt nanoparticles which facilitated more active sites for reaction, the Pt-loaded NRGO photocatalytically generated H₂ gas ten times higher than that of Pt-loaded RGO when coupled with photoactive graphitic carbon nitride (g-C₃N₄).