Prakash Ramakrishnan

Zinc–Air Battery: Understanding the Structure and Morphology Changes of Graphene-Supported CoMn2O4 Bifunctional Catalysts Under Practical Rechargeable Conditions

Nitrogen-doped/undoped thermally reduced graphene oxide (N-rGO) decorated with CoMn2O4 (CMO) nanoparticles were synthesized using a simple one-step hydrothermal method. The activity and stability of this hybrid catalyst were evaluated by preparing air electrodes with both primary and rechargeable zinc-air batteries that consume ambient air. Further, we investigated the relationship between the physical properties and the electrochemical results for hybrid electrodes at various cycles using X-ray diffraction, scanning electron microscopy, galvanodynamic charge-discharging and electrochemical impedance spectroscopy. The structural, morphological and electrocatalytic performances confirm that CMO/N-rGO is a promising material for safe, reliable, and long-lasting air cathodes for both primary and rechargeable zinc-air batteries that consume air under ambient condition.

Three-dimensional hierarchical nitrogen-doped arch and hollow nanocarbons: morphological influences on supercapacitor applications

We report nitrogen (N) doped nanocarbons with two different morphologies, arch and hollow structure, for supercapacitor (SC) application. A simple co-axial electrospinning approach and subsequent leaching and carbonization processes are employed to fabricate N-doped carbon nanostructures. The fabricated N-doped arch and hollow nanocarbons exhibit high N-contents of 9.02 and 8.73 wt%, high surface areas of 619 and 557 m2 g−1, and total pore volumes of 0.6589 and 0.5681 cm3 g−1, respectively. The N-doped arch and hollow nanocarbons exhibit the maximum specific capacitances (Csp) of 417 and 371 F g−1 at 2 mV s−1 in a three-electrode system and Csp values of 230 and 212 F g−1 at 2 mV s−1 for a two-electrode system, respectively, in 1 M H2SO4 solution. The maximum energy densities of 8.4 and 7.5 W h kg−1 are obtained for N-doped arch and hollow nanocarbons, respectively. Further, these novel carbon nanostructures also deliver good cycle stabilities of 98% for 5000 cycles at a current density of 1 A g−1. Such outstanding SC electro-sorption ability is due to the high micro-texture and high N-content characteristics of carbon nanostructures.

Nitrogen-doped arch and hollow shaped nanocarbons for CO2 adsorption

We report arch and hollow nanocarbons with high nitrogen content and appreciable surface area that are highly capable of adsorbing CO2 (4.23 mmol g−1), are selective (CO2/N2: ∼13%) and have high facile regeneration properties (98%) under ambient conditions, respectively.

Dual Heteroatom-Doped Carbon Nanofoam-Wrapped Iron Monosulfide Nanoparticles: An Efficient Cathode Catalyst for Li–O2 Batteries

Cost-effective dual heteroatom-doped 3D carbon nanofoam-wrapped FeS nanoparticles (NPs), FeS-C, act as efficient bifunctional catalysts for Li-O2 batteries. This cathode exhibits a maximum deep discharge capacity of 14 777.5 mA h g-1 with a 98.1 % columbic efficiency at 0.1 mA cm-2 . The controlled capacity (500 mA h g-1 ) test of this cathode delivers a minimum polarization gap of 0.73 V at 0.1 mA cm-2 and is sustained for 100 cycles with an energy efficiency of approximately 64 % (1st cycle) and 52 % (100th cycle) at 0.3 mA cm-2 , under the potential window of 2.0-4.5 V. X-ray photoelectron spectroscopy reveals the substantial reversible formation and complete decomposition of Li2 O2 . The excellent recharging ability, high rate performance, and cycle stability of this catalyst is attributed to the synergistic effect of FeS catalytic behavior and textural properties of heteroatom-doped carbon nanostructures.