Facile Synthesis of Ni-MgO/CNT Nanocomposite for Hydrogen Evolution Reaction.

In this study, the pristine MgO, MgO/CNT and Ni-MgO/CNT nanocomposites were processed using the impregnation and chemical vapor deposition methods and analyzed for hydrogen evolution reaction (HER) using the electrochemical water splitting process. Furthermore, the effect of nickel on the deposited carbon was systematically elaborated in this study. The highly conductive carbon nanotubes (CNTs) deposited on the metal surface of the Ni-MgO nanocomposite heterostructure provides a robust stability and superior electrocatalytic activity. The optimized Ni-MgO/CNT nanocomposite exhibited hierarchical, helical-shaped carbon nanotubes adorned on the surface of the Ni-MgO flakes, forming a hybrid metal-carbon network structure. The catalytic HER was carried out in a 1M alkaline KOH electrolyte, and the optimized Ni-MgO/CNT nanocomposite achieved a low (117 mV) overpotential value (ɳ) at 10 mA cm-2 and needed a low (116 mV/dec) Tafel value, denotes the Volmer-Heyrovsky pathway. Also, the high electrochemical active surface area (ECSA) value of the Ni-MgO/CNT nanocomposite attained 515 cm2, which is favorable for the generation of abundant electroactive species, and the prepared electrocatalyst durability was also performed using a chronoamperometry test for the prolonged duration of 20 h at 10 mA cm-2 and exhibited good stability, with a 72% retention. Hence, the obtained results demonstrate that the optimized Ni-MgO/CNT nanocomposite is a highly active and cost-effective electrocatalyst for hydrogen energy production.

Direct Growth of Binder-Free CNTs on a Nickel Foam Substrate for Highly Efficient Symmetric Supercapacitors.

In the modern civilized world, energy scarcity and associated environmental pollution are the center of focus in the search for reliable energy storage and harvesting devices. The need to develop cheaper and more competent binder-free electrodes for high-performance supercapacitors has attracted considerable research attention. In this study, two different procedures are followed to enhance the growth of carbon nanotubes (CNT-E and CNT-NF) directly coated on a Ni-foam substrate by a well-functioning chemical vapor deposition (CVD) method. Thus, directly grown optimized CNT electrodes are used as electrodes for electrochemical devices. Furthermore, solid-state symmetric supercapacitors are fabricated using CNT-NF//CNT-NF, and fruitful results are obtained with maximum specific capacitance (250.51 F/g), energy density (68.19 Wh/kg), and power density (2799.77 W/kg) at 1 A/g current density. The device exhibited good cyclic stability, with 92.42% capacitive retention and 99.68% Coulombic efficiency at 10 000 cycles, indicating the suitability of the electrodes for practical applications. This study emphasizes the importance of studying the direct growth of binder-free CNT electrodes to understand the actual behavior of electrodes and the proper storage mechanism.

Quaternary Cu2FeSnS4/PVP/rGO Composite for Supercapacitor Applications.

Electrochemical energy storage is a current research area to address energy challenges of the modern world. The Cu2FeSnS4/PVP/rGO-decorated nanocomposite using PVP as the surface ligand was explored in a simple one-step solvothermal route, for studying their electrochemical behavior by designing asymmetric hybrid supercapacitor devices. The full cell three-electrode arrangements delivered 748 C/g (62.36 mA h/g) at 5 mV/s employing CV and 328 F/g (45.55 mA h/g) at 0.5 A/g employing GCD for the Cu2FeSnS4/PVP/rGO electrode. The half-cell two-electrode device can endow with 73 W h/kg and 749 W/kg at 1 A/g energy and power density. Furthermore, two Cu2FeSnS4/PVP/rGO//AC asymmetric devices connected in series for illuminating a commercial red LED more than 1 min were explored. This work focuses the potential use of transition-metal chalcogenide composite and introduces a new material for designing high-performance supercapacitor applications.