Beyond the ordinary: exploring the synergistic effect of iodine and nickel doping in cobalt hydroxide for superior energy storage applications.

This study explores the iodine and nickel-doped cobalt hydroxide (I & Ni-co-doped-Co(OH)2) as a potential material for energy storage and conversion applications owing to its excellent electrochemical characteristics. According to our analysis, it was revealed that this material exhibits pseudocapacitive-like behavior, as evident from distinct redox peaks observed in cyclic voltammetry, which confirms its ability to store charges. The diffusion coefficient analysis reveals that this material possesses conductivity and rapid diffusion kinetics, making it particularly advantageous compared to materials synthesized in previous studies. Charge-discharge measurements were performed to analyze the charge storage capacity and stability of this material after 3000 consecutive cycles, showing its excellent stability with minimum loss of capacitance. Furthermore, its anodic and cathodic linear sweep voltammetry curves were measured to evaluate its oxygen evolution and hydrogen evolution reaction performance. The results showed that the material exhibited an excellent water splitting performance, which suggests its potential practical application for hydrogen production. This increased activity was attributed to the doping of α-Co(OH)2, which improved its structural stability, electrical conductivity, and charge transfer efficiency. Thus, I & Ni-co-doped-Co(OH)2 possesses enhanced properties that make it an excellent material for both energy storage and hydrogen generation applications.

Large-scale sonochemical fabrication of a Co3O4-CoFe2O4@MWCNT bifunctional electrocatalyst for enhanced OER/HER performances.

Herein, we have prepared a mixed-phase Co3O4-CoFe2O4@MWCNT nanocomposite through a cheap, large-scale, and facile ultrasonication route followed by annealing. The structural, morphological, and functional group analyses of the synthesized catalysts were performed by employing various characterization approaches such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The resultant samples were tested for bifunctional electrocatalytic activity through various electrochemical techniques: cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The prepared Co3O4-CoFe2O4@MWCNT nanocomposite achieved a very high current density of 100 mA cm-2 at a lower (290 mV and 342 mV) overpotential (vs. RHE) and a smaller (166 mV dec-1 and 138 mV dec-1) Tafel slope in the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, compared to Co3O4-CoFe2O4. The excellent electrochemical activity of the as-prepared electrocatalyst was attributed to the uniform incorporation of Co3O4-CoFe2O4 over MWCNTs which provides high redox active sites, a greater surface area, better conductivity, and faster charge mobility. Furthermore, the enhanced electrochemical active surface, low charge-transfer resistance (Rct), and higher exchange current density (J0) of the Co3O4-CoFe2O4@MWCNT ternary composite are attributed to its superior behavior as a bifunctional electrocatalyst. Conclusively, this study demonstrates a novel and large-scale synthesis approach for bifunctional electrocatalysts with a high aspect ratio and abundance of active sites for high-potential energy applications.

An efficient and stable iodine-doped nickel hydroxide electrocatalyst for water oxidation: synthesis, electrochemical performance, and stability.

The design of oxygen evolution reaction (OER) catalysts with higher stability and activity by economical and convenient methods is considered particularly important for the energy conversion technology. Herein, a simple hydrothermal method was adopted for the synthesis of iodine-doped nickel hydroxide nanoparticles and their OER performance was explored. The electrocatalysts were structurally characterized by powder X-ray diffraction analysis (P-XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and BET analysis. The electrochemical performance of the electrocatalysts was assessed by cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy. The abundant catalytic active sites, oxygen vacancies, low charge-transfer resistance, and a high pore diameter to pore size ratio of iodine-doped Ni(OH)2 were responsible for its excellent catalytic activity, whereby OER was initiated even at 1.52 V (vs. RHE) and a 330 mV overpotential was needed to reach a 40 mV cm-2 current density in 1 M KOH solution. The material also exhibited a low Tafel slope (46 mV dec-1), which suggests faster charge-transfer kinetics as compared to its counterparts tested under the same electrochemical environment. It is worth noting that this facile and effective approach suggests a new way for the fabrication of metal hydroxides rich in oxygen vacancies, thus with the potential to boost the electrochemical performance of energy-related systems.