Regulating oxygen vacancies in Co3O4 by combining solution reduction and Ni2+ impregnation for oxygen evolution reaction

Oxygen vacancies are considered to be an important factor to influence the electronic structure and charge transport of electrocatalysts in the field of energy chemistry. Various strategies focused on oxygen vacancy engineering are proved to be efficient for further improving the electrocatalytic performance of Co3O4. Herein, an optimal Co3O4 with rich oxygen vacancies have been synthesized via a two-step process combining solution reduction and Ni2+ impregnation. The as-prepared electrocatalyst exhibits an enhanced oxygen evolution performance with the overpotential of 330 mV at the current density of 10 mA cm−2 in alkaline condition, which is 84 mV lower than that of pristine one. With the increasing of oxygen vacancies , the charge transfer efficency and surface active area are relatively enhanced reflected by the Tafel slope and double-layer capacitance measurement. These results indicate that combining solution reduction and heteroatom doping can be a valid way for efficient metal oxides-based electrocatalyst development by constructing higher concentration of oxygen vacancy.

Production of a new 3D electrode skeleton of Ni with very high electrochemical surface area for oxygen evolution

Long and stable fibers (Tapes) of nickel with a thickness that can reach less than one hundred nanometers were produced through directional solidification of Ni-Al hypereutectic alloy on the surface of Ni and then, leaching the alloy in potassium hydroxide solution. Experimental results illustrated that the structure of the tapes is Raney nickel. In other words, a 3D structure consisting of a large number of Nano-dimensional tapes with a Nano-porous and Nano-crystalline structure was created. The activity of this structure was evaluated for oxygen evolution in alkaline media. The results showed that by increasing the number of Tapes per 〖cm〗^2 (density of Tapes), electrochemical surface area and double layer capacitance increase. As the density of Tapes increases, the OER overpotential decreases, but with further increase in density of Tapes, the OER overpotential increases again. Re-increase in overpotential was associated to trapping of oxygen bubbles. The best sample showed an overpotential 240 mV at 10 mA/〖cm〗^2 and 350 mV at 500 mA/〖cm〗^2. Also, this sample worked without any sign of degradation at 500 mA/〖cm〗^2 for 6 days (144 hours).

Coating activated carbon from coconut shells with Co3O4/CeO2 for high-performance supercapacitor applications: An experimental study

Activated carbon from coconut shells is a low-cost, environmentally friendly material that is available for fabricating the electrodes for electric double-layer capacitance supercapacitors. As such, activated carbon derived from coconut shells was coated with Co3O4/CeO2, and its electrical and ionic conductivity were evaluated. The ternary technique for selecting materials was systematically investigated with an economical process. The Co3O4/CeO2 coating that was formed on the activated carbon coconut shells was deemed AC-Co3O4-CeO2. The 90-05-05 composite was the best electrode for electric double-layer capacitance supercapacitors, resulting in high conductivity (0.62 x 103 S·cm2), low series resistance and internal resistance (based on the Nyquist plot), and the charge-discharge was able to reach 0.56 V for 90 seconds (1A/g). Therefore, activated carbon coconut shells coated in Co3O4/CeO2 can promote the necessary characteristics of electrodes needed for electric double-layer capacitance supercapacitors.

Corrosion Resistance of Epoxy Coatings Modified by Bis-Silane Prepolymer on Aluminum Alloy

In this communication, a bis-silane prepolymer was used to modify epoxy resin, aiming to enhance the corrosion resistance of epoxy coatings on aluminum alloy substrates. The bis-silane prepolymer was prepared by tetraethoxysilane (TEOS) and γ-glycidoxypropyl trimethoxysilane (GPTMS). The corrosion behavior of silane-epoxy coatings was studied. Compared with silane monomer-modified epoxy coatings, bis-silane-modified epoxy coatings have lower coating capacitance (Cc), higher charge transfer resistances (Rdl), and lower double layer capacitance (Cdl) during long-time immersion. It indicates that bis-silane-modified epoxy coating has stronger waterproof permeability and substrate corrosion protection ability. In addition, due to the leaching of the silane component and cross-linking reaction between different silanes during the immersion process, the bis-silane-modified epoxy coatings exhibit much stronger “self-healing” ability.