A study of the detonation synthesis method to make graphene and the properties of the resulting graphene is presented. The gaseous precursors are mixtures of oxygen and acetylene with oxygen/carbon molar ratios of O/C = 0.25 to 0.75. Chamber pressure and temperature data indicate pressures ≤ 300 psi and temperatures of 2550 ± 100K after initiation of the reaction mixture. The graphene material collected from the chamber after the detonation was characterized by Raman, XRD (X‐ray diffraction), BET, SEM (scanning electron microscopy), TEM (transmission electron microscopy), and so on. The material properties divide into two groups: low O/C (≤ 0.45) and high O/C (≥ 0.5). Low O/C graphene appears as a low density, aerosol gel with ∼8 weakly associated, disordered turbostratic layers with a lateral extent of 20 to 30 nm. High O/C graphene appears as a denser powder with ∼30 weakly associated turbostratic layers, with a lateral extent of 100 to 200 nm. We conclude, as we have previously, that the high detonation temperature during the reaction is the primary reason that graphene is formed rather than soot. Differentiation into two types of graphene products is hypothesized to be a result of aggregation kinetics to form a static gel that pre‐empts layering (stacking) when O/C is low.

The advances in the mass scale manufacturing of microscale energy storage devices via inkjet printing rely on the development of high-quality printable ink. The earth-abundant, nontoxic carbon materials such as graphene, carbon nanotube (CNT), reduced graphene oxide (r-GO) have shown excellent electrochemical performance and thus garnered significant interest as suitable electrode material. Here we report the formulation of printable graphene aerogel ink and the fabrication of the micro-supercapacitors (μ-SCs) on flexible polyimide substrates via inkjet printing method. The advantage of using pristine graphene aerogel intends to avoid the complex processing steps and the use of toxic chemicals in the ink formulation and lower the concentration of other additive components. Thus, a higher loading of active functional material in the printable ink is achieved. The aerogel ink directly employed to write the interdigitated μ-SCs devices on a flexible polyimide substrate at room temperature via inkjet printing. The electrochemical performance measured using the organic ionic liquid in the voltage range of 0-1 volt. These printed μ-SCs showed an areal capacity of 55 μF/cm 2 at a current density of 6 micro-amp/cm 2 . The printed devices showed good stability, with ~80% of capacity retention after 10,000 cycles. Contrary to the graphenebased μ-SCs, the aerogel micro-supercapacitors do not show a significant distortion in the CV scan even at a very high scan rate of ~2Vs -1 . Thus, we propose graphene aerogel as promising electrode material for mass-scale production of the μ-SCs.

This study reports the superior performance of graphene nanosheet (GNS) materials over Vulcan XC72 incorporated as cathode catalyst in Li-O2 battery. The GNSs employed were synthesized from a novel, eco-friendly and cost-effective technique involving chamber detonation of oxygen and acetylene precursors. Two GNS catalysts i.e., GNS-1 and GNS-2 fabricated with 0.3 and 0.5 O/C precursor molar ratios, respectively, were utilized. Specific surface area (SSA) analysis revealed significantly higher SSA and total pore volume for GNS-1 (180 m2 g−1, 0.505 cm3 g−1) as compared with GNS-2 (19 m2 g−1, 0.041 cm3 g−1). GNS-1 exhibited the highest discharge capacity (4.37 Ah g−1) and superior cycling stability compared with GNS-2 and Vulcan XC72. Moreover, GNS-1 showed promising performance at higher current densities (0.2 and 0.3 mA cm−2) and with various organic electrolytes. The superior performance of GNS-1 can be ascribed to its higher mesopore volume, SSA and optimum wettability compared to its counterparts.

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