S.J. Richard Prabakar

SnO2/Graphene Composites with Self‐Assembled Alternating Oxide and Amine Layers for High Li‐Storage and Excellent Stability

An alternating stack (SG/GN) consisting of SnO₂-functionalized graphene oxide (SG) and amine-functionalized GO (GN) is prepared in solution. The thermally reduced SG/GN (r(SG/GN)) with decreased micro-mesopores and completely eliminated macropores, results in a high reversible capacity and excellent capacity retention (872 mA h g⁻¹ after 200 cycles at 100 mA g⁻¹) when compared to a composite without GN.

Highly crystalline Prussian blue/graphene composites for high-rate performance cathodes in Na-ion batteries

We report the synthesis of highly crystalline Prussian Blue (PB) embedded in graphene oxide (GO) layers and its superior electrochemical properties. Highly crystalline PB is prepared from Fe2O3 nanoparticles anchored on GO (Fe2O3/GO). Regulated Fe3+-ion release and slow crystallization with [Fe(CN)6] in the vicinity of Fe2O3/GO produce a GO-interconnected PB (HC-PB/GO) with fewer [Fe(CN)6] vacancies and H2O molecules. When compared with PB synthesized under identical conditions without GO, the HC-PB/GO delivers a noticeably higher reversible capacity and better cyclability as a cathode in Na-ion batteries (SIBs). The improvement in high-rate performance is rather striking. While the energy density of PB at a charge/discharge (C/D) rate of 2.0 A g−1 is negligible, the HC-PB/GO delivers 280 mW h g−1. The increase of electronic conduction and Na+ ion diffusion in HC-PB/GO contribute to a substantial improvement in rate capability.

Graphene oxide self-assembled with a cationic fullerene for high performance pseudo-capacitors

Control of the microstructures of graphene oxide (GO) is realized by introducing a cationic fullerene (CFU), resulting in a high-performance pseudo-capacitor. The strong electrostatic interaction between anionic GO and the CFU produces a self-assembled composite (GO/CFU), in which the CFU units intervene to form randomly stacked GO layers. The CFU acts as a spacer between GO layers, allowing a significant fraction of the oxygen-functional groups of GO to be redox-active. When tested as a pseudo-capacitor in 1.0 M H2SO4, the optimized GO/CFU composite delivers a capacitance of 357 F g−1 at 0.4 A g−1, in contrast to 160 F g−1 for GO alone, which is one of the greatest values reported for graphene composites with electro-inactive carbonaceous entities. The improvement in the capacitance by CFU incorporation is also evidenced at a high charge/discharge rate (285 and 137 F g−1 at 5 A g−1 for GO/CFU and GO, respectively). As a result, the GO/CFU composite delivers an energy density of 40 W h kg−1 and a power density of 2793 W kg−1 at 5 A g−1, in contrast to 19 W h kg−1 and 2748 W kg−1 for GO alone. During 5000 charge/discharge cycles at 5 A g−1, the capacitance of the GO/CFU composite increases slightly (4% increase in GO/CFU vs. 4% decrease in GO), which validates the effectiveness of a self-assembly strategy for high performance supercapacitor applications.

Simultaneous Suppression of Metal Corrosion and Electrolyte Decomposition by Graphene Oxide Protective Coating in Magnesium-Ion Batteries: Toward a 4-V-Wide Potential Window

Despite remarkable developments in electrolyte systems over the past 2 decades, magnesium-ion batteries still suffer from corrosion susceptibility and low anodic limits. Herein we describe how graphene oxide (GO), coated onto non-noble metals (Al, Cu, and stainless steel) via electrophoretic deposition, can solve this problem. In all phenyl complex electrolytes, GO coating results in a significant suppression of corrosion and extends the anodic limits (up to 4.0 V vs Mg/Mg2+) with no impact on reversible Mg plating/stripping reactions. The same effect of GO coating is also established in magnesium aluminum chloride complex electrolytes. This remarkable improvement is associated with the electrostatic interaction between the ionic charges of electrolytes and the surface-functional groups of GO. In addition, GO coating does not aggravate the cathode performance of Mo6S8, which allows the use of non-noble metals as current collectors. We also discuss the role of GO in increasing anodic limits when it is hybridized with α-MnO2.