Integrated approaches that expedite the production and processing of graphene into useful structures and devices, particularly through simple and environmentally friendly strategies, are highly desirable in the efforts to implement this two-dimensional material in state-of-the-art electrochemical energy storage technologies. Here, we introduce natural nucleotides (e.g., adenosine monophosphate) as bifunctional agents for the electrochemical exfoliation and dispersion of graphene nanosheets in water. Acting both as exfoliating electrolytes and colloidal stabilizers, these biomolecules facilitated access to aqueous graphene bio-inks that could be readily processed into aerogels and inkjet-printed interdigitated patterns. Na-O2 batteries assembled with the graphene-derived aerogels as the cathode and a glyme-based electrolyte exhibited a full discharge capacity of ∼3.8 mAh cm–2 at a current density of 0.2 mA cm–2. Moreover, shallow cycling experiments (0.5 mAh cm–2) boasted a capacity retention of 94% after 50 cycles, which outperformed the cycle life of prior graphene-based cathodes for this type of battery. The positive effect of the nucleotide-adsorbed nanosheets on the battery performance is discussed and related to the presence of the phosphate group in these biomolecules. Microsupercapacitors made from the interdigitated graphene patterns as the electrodes also displayed a competitive performance, affording areal and volumetric energy densities of 0.03 μWh cm–2 and 1.2 mWh cm–3 at power densities of 0.003 mW cm–2 and 0.1 W cm–3, respectively. Taken together, by offering a green and straightforward route to different types of functional graphene-based materials, the present results are expected to ease the development of novel energy storage technologies that exploit the attractions of graphene.

Printed networks of insulating two-dimensional (2D) materials are promising for dielectric applications in printed electronic devices. However, this work has not really progressed beyond networks of boron nitride (BN) nanosheets displaying dielectric constants of <6. Here we use liquid-phase exfoliation to demonstrate the production of nanosheets from the high-permittivity, layered material bismuth oxychloride (BiOCl). We first demonstrate liquid exfoliation of BiOCl nanosheets followed by the characterization of the resultant suspensions. We then use aerosol jet printing to print capacitors from patterned heterostacks, consisting of BiOCl nanosheet networks sandwiched between networks of liquid-exfoliated graphene nanosheets. We characterize these capacitors as a function of network thickness, finding a high-network dielectric constant of >40 but a relatively low dielectric strength of 0.67 MV/cm. We also observe an unexpected series capacitance, which we attribute to an internal capacitance associated with inter-nanosheet junctions within the graphene electrodes.

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