A simple approach for growing porous electrochemically reduced graphene oxide (pErGO) networks on copper wire, modified with galvanostatically deposited copper foam is demonstrated. The as-prepared pErGO networks on the copper wire are directly used to fabricate solid-state supercapacitor. The pErGO-based supercapacitor can deliver a specific capacitance (Csp) as high as 81±3 F g−1 at 0.5 A g−1 with polyvinyl alcohol/H3PO4 gel electrolyte. The Csp per unit length and area are calculated as 40.5 mF cm−1 and 283.5 mF cm−2, respectively. The shape of the voltammogram retained up to high scan rate of 100 V s−1. The pErGO-based supercapacitor device exhibits noticeably high charge-discharge cycling stability, with 94.5% Csp retained even after 5000 cycles at 5 A g−1. Nominal change in the specific capacitance, as well as the shape of the voltammogram, is observed at different bending angles of the device even after 5000 cycles. The highest energy density of 11.25 W h kg−1 and the highest power density of 5 kW kg−1 are also achieved with this device. The wire-based supercapacitor is scalable and highly flexible, which can be assembled with/without a flexible substrate in different geometries and bending angles for illustrating promising use in smart textile and wearable device.

Carbonaceous materials with high surface area and a sheet-like structure promote fast ion-transport kinetics, making them an ideal choice to be used in supercapacitors. Few-layer graphene (FLG)-like nanosheets with abundance of micro as well as mesopores are achieved via mechanical exfoliation method from an agricultural waste biomass: peanut shell (PS). A well-known elementary method of probe-sonication, for the achievement of FLG sheets from renewable sources, is introduced in this study for the very first time. The Peanut shell-derived FLG (PS-FLG) possesses remarkably high specific surface area (2070 m2 g−1) with a sufficiently large pore volume of 1.33 cm3 g−1. For the fabrication of a binder-free supercapacitor, the PS-FLG-based electrodes exhibited a high specific capacity of 186 F g−1 without the use of any binder in 1 M H2SO4 as supporting electrolyte. The highest energy density of 58.125 W h Kg−1 and highest power density of 37.5 W Kg−1 was achieved by the material. Surprisingly, the working potential increased to 2.5 V in an organic electrolyte leading to an obvious increase in the energy density to 68 W h Kg−1. Solid-state-supercapacitor was fabricated with this material for the possible use of low-cost, high energy promising energy storage device.

We describe the development of a highly sensitive amperometric biosensor based on the hybrid material derived from nanoscale Pt particles (nPt) and graphene for the sensing of H 2 O 2 and cholesterol. The biosensing platform was developed using the hybrid material and enzymes cholesterol oxidase and cholesterol esterase. Chemically synthesized graphene has been decorated with nanosized Pt particles. The electron microscopic measurements show that the Pt nanoparticles on graphene have an average size of 12 nm and are randomly distributed throughout the surface. The Pt nanoparticle based hybrid material modified electrode efficiently catalyzes the electrochemical oxidation of H 2 O 2 at the potential of 0.4 V, which is >100 mV less positive with respect to the bulk Pt electrode. The sensing platform is highly sensitive and shows linear response toward H 2 O 2 up to 12 mM with a detection limit of 0.5 nM [S/N (signal-to-noise ratio) ) 3] in the absence of any redox mediator or enzyme. The combination of electronically highly conductive graphene and catalytically active Pt nanoparticle favors the facilitated electron transfer for the oxidation of H 2 O 2 . The cholesterol biosensor was developed by immobilizing cholesterol oxidase and cholesterol esterase on the surface of graphene-nanoparticle hybrid material. The bienzyme integrated nanostructured platform is very sensitive, selective toward cholesterol, and it has a fast response time. The sensitivity and limit of detection of the electrode toward cholesterol ester are 2.07 ( 0.1 µA/µM/cm 2 and 0.2 µM, respectively. The apparent Michaelis-Menten constant (K m app ) was calculated to be 5 mM. The sensor does not suffer from the interference due to other common electroactive species and is highly stable. The analytical performance of the hybrid material was further evaluated using screen-printed electrodes with 50 µL of electrolyte.

A rapid and facile route for the synthesis of reduced graphene oxide sheets (rGOs) at room temperature by the chemical reduction of graphene oxide using Zn/acid in aqueous solution is demonstrated.

An effective modulation of the active sites in a bifunctional electrocatalyst is essentially desired, and it is a challenge to outperform the state-of-the-art catalysts toward oxygen electrocatalysis. Herein, we report the development of a bifunctional electrocatalyst having target-specific Fe–N4/C and Co–N4/C isolated active sites, exhibiting a symbiotic effect on overall oxygen electrocatalysis performances. The dualism of N-dopants and binary metals lower the d-band centers of both Fe and Co in the Fe,Co,N–C catalyst, improving the overpotential of the overall electrocatalytic processes (ΔE ORR‑OER = 0.74 ± 0.02 V vs RHE). Finally, the Fe,Co,N–C showed a high areal power density of 198.4 mW cm–2 and 158 mW cm–2 in the respective liquid and solid-state Zn–air batteries (ZABs), demonstrating suitable candidature of the active material as air cathode material in ZABs.