Graphene Quantum Dots Supported by Graphene Nanoribbons with Ultrahigh Electrocatalytic Performance for Oxygen Reduction

Abstract

A new class of oxygen reduction reaction (ORR) catalysts based on graphene quantum dots (GQDs) supported by graphene nanoribbons (GNRs) has been developed through a one-step simultaneous reduction reaction, leading to ultrahigh performance for O reduction with an excellent electrocatalytic activity (higher limiting current density and lower overpotential than those of platinum) and high selectivity and stability in alkaline media comparable to the best C-based ORR catalysts reported so far. Electron microscopy revealed numerous surface/edge defects on the GQD/GNR surfaces and at their interface to act as the active sites. This, coupled with efficient charge transfer between the intimately contacted GQDs and GNRs, rationalized the observed ultrahigh electrocatalytic performance for the resultant GQD-GNR hybrids. Thus, this study opens a new direction for developing low-cost, highly efficient, C-based ORR electrocatalysts.

Carbon-Based Metal-Free Electrocatalysis for Energy Conversion, Energy Storage, and Environmental Protection

“…Well-defined pore distributions and defects can affect the catalytic activity of carbon-based catalysts [111,112,[119][120][121][122]. In 2015, Jin et al reported a new class of ORR catalysts based on graphene quantum dots supported by graphene nanoribbons with ORR performances comparable to or even better than that of Pt/C electrodes [119].…”

“…In 2015, Jin et al reported a new class of ORR catalysts based on graphene quantum dots supported by graphene nanoribbons with ORR performances comparable to or even better than that of Pt/C electrodes [119]. These performances were attributed to the presence of numerous edge defects on quantum dots and Fig.…”

“…In addition, edge-rich and dopant-free CNTs and graphene were developed as highly efficient ORR electrocatalysts [126], and the activity origin of aerobic oxidation in porous graphene oxide (GO) catalysts was elucidated to be caused by edge sites with unpaired electrons and carboxylic groups favorable for O 2 trapping and electron transport. Recent developments in defective carbon catalysts have demonstrated the critical role of edge and intrinsic defects in regulating catalytic performance of carbon catalysts [94,119], and this is an area that will clearly benefit from further research.…”

The New Graphene Family Materials: Synthesis and Applications in Oxygen Reduction Reaction

“…Due to their intrinsic properties, such as abundant edges, thin walls, high surface area and excellent electrical conductivity, GNRs are extremely attractive to enhance the ORR activity [110][111][112][113][114][115][116][117][118]. In Liu's group, they used longitudinal unzipping technology to produce GNRs from CNTs [110].…”

Recent Advances in Heteroatom-Doped Graphene Materials as Efficient Electrocatalysts towards the Oxygen Reduction Reaction

“…19 Moreover, nitrogen doping in the monolayer graphene induces the Fermi level shifting above the Dirac point and suppresses the density of state near the Fermi level, thus opening the band gap between the conduction band and valence band. Very recently, it has been reported that metal-free N-doped carbons exhibit excellent ORR catalytic activity, which is comparable to or better than commercial Pt/C catalysts, 28,34 illustrating an exceptional progress on metal-free catalysts used in metal-air batteries or fuel cells. For example, Ding et al presented a novel strategy for the selective synthesis of pyridinic-and pyrrolic-nitrogen-doped graphene (NG) by the use of layered montmorillonite (MMT) as a quasi-closed flat nanoreactor, as shown in Figure 4.…”