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Nitrogen-enriched graphene was fabricated via a facile strategy. Graphene oxide (GO) nanosheets and graphene oxide quantum dots (GQDs) were used as a structure-directing agent and in situ activating agent, respectively, after photoreduction under NH 3 atmosphere. The combination of photoreduction and NH 3 not only reduced GO and GQD composites (GO/GQDs) within a shorter duration but also doped a high level of nitrogen on the composites (NrGO/GQDs). The nitrogen content of NrGO/GQDs reached as high as 18.86 at% within 5 min of irradiation. Benefiting from the nitrogen-enriched GO/GQDs hybrid structure, GQDs effectively prevent the agglomeration of GO sheets and increased the numbers of ion channels in the material. Meanwhile, the high levels of nitrogen improved electrical conductivity and strengthened the binding energy between GQD and GO sheets. Compared with reduced GO and low nitrogen-doped reduced GO, NrGO/GQD electrodes exhibited better electrochemical characteristics with a high specific capacitance of 344 F g −1 at a current density of 0.25 A g −1 . Moreover, the NrGO/GQD electrodes exhibited 82% capacitance retention after 3000 cycles at a current density of 0.8 A g −1 in 6 M KOH electrolyte. More importantly, the NrGO/GQD electrodes deliver a high energy density of 43 Wh kg −1 at a power density of 417 W kg −1 in 1 M Li 2 SO 4 electrolyte. The nitrogen-doped graphene and corresponding supercapacitor presented in this study are novel materials with potential applications in advanced energy storage systems.

In metal-free g-C3N4 based materials, the rapid recombination of photoexcited carriers limits its photocatalytic activity. In this work, for the first time, we synthesized a new kind of diatomic-doped graphene quantum dots (GQDs), namely, nitrogen and phosphorus co-doped GQDs (NP-GQDs), and then loaded on g-C3N4 surface to obtain NP-GQDs/g-C3N4 composite photocatalyst. Under visible and ultraviolet irradiation, the MO photodegradation rate of NP-GQDs/g-C3N4 is as high as 97.5% and 96%, respectively, which was 1.71 and 1.85 times higher than that of pure g-C3N4. The remarkable enhancement of photodegradation activity is mainly attributed to the introduction of NP-GQDs could promote the formation, transportation and separation of photoexcited carriers. Furthermore, the photocatalyst exhibits outstanding recycle stability without a significant decrease in activity after three reused runs. This study provides a new understanding of the roles played by diatomic-doped graphene quantum dots in photocatalytic systems and provides a new prospect in developing highly efficient g-C3N4-based photocatalysts.

As an ultrathin transport layer, graphene-based materials play an increasingly important role in perovskite optoelectronics. Full comprehension of the carrier transfer process between them is of great significance, however, seldom attention has been paid to how the carrier transfer, from graphene derivative to perovskite, affects the physical property of perovskite. Here, we report that CsPbBr3 and CsPbI3 QDs produce a Burstein-Moss type photoluminescence (PL) blueshift arisen from the electron transfer from graphene oxide (GO), and in CsPbI3 QDs this effect is highly notable, ~50 meV. Such results indicate that perovskite QDs is highly optically sensitive to the electron injection, and quite promising in optoelectronic modulator applications.