Preparation Of Cobalt-Based(Hydroxide)Oxide Electrode Materils And Their Properties Toward Electrochemical Oxidation

The development and utilization of renewable and clean energy such as solar and wind energy is a target which people concern and pursuit. Electrolysis of water makes it possible to achieve the conversion between electrical energy and chemical energy, which provide resource in the form of hydrogen energy. It has the characteristics of high energy density and no carbon emission upon the release of energy stored, thus is considered to be one of the most appealing strategies for achieving clean energy. Currently, there are many studies focused on the development of efficient electrocatalyst to promote the reaction and accelerate the dynamics.In our research, we developed non-precious, relatively abundant transition metallic Cobalt-based (hydroxide) oxide structural catalysts, and made a systematic study of the influence of their structure and composition on the water-splitting half reaction——water oxidation catalytic property, the main contents are as follows:1. Cobalt hydroxide precursor was firstly grown on the conductive nickel alloy foil by means of mild hydrothermal method, then six rounded Co3O4crystallite was obtained after heat treatment under certain conditions. After that, Dipping the Co34@Ni electrode into Cobalt salts of appropriate concentration for surface modification with the impregnation method, in order to build a Co3O4@Ni electrocatalyst with homojunction, and it was used for the electrooxidation of water. The formed homojunction electrocatalyst has enlarged active surface area as well as increased roughness factor, they exhibits enhanced electrocatalytic property toward water oxidation under alkaline condition. When the overpotential is328mV, TOF value of the homojunction Co3O4@Ni catalytic material is0.03s-1, higher than that of a previously reported excellent Co3O4electrocatalyst (0.0187s-1) at the same overpotential. The strengthened catalytic ability is attributed to the roughened surface which results from homojunction, thus increases the contact between the active sites and reaction species.2. Binary zinc-cobalt layered double hydroxide (ZnCo-LDH) films were directly grown on a conductive Nickel foil by electrodeposition method at room temperature. The ZnCo-LDH films were composed of oriented nanowalls whose ab plane was vertical to the substrate, and the two-dimensional (2D) LDH nanosheets acted as fundamental units for the nanowall building. ZnCo-LDH exhibited excellent catalytic activity for electrochemical water oxidation in alkali solution. The onset overpotential of the optimal LDH catalyst for oxygen-evolving reaction is0.33V in a0.1M KOH aqueous solution, superior to those well-known Cobalt hydroxide and particle Co3O4electrocatalysts. The turnover frequencies (TOFs) of LDH catalysts show a linear dependence on the overpotentials, higher than that of monometallic cobalt hydroxide at the overpotential beyond0.55V. For instance, at the overpotential of0.7V, the TOF value of the optimal LDH reaches3.56s1,1.7times higher than that of monometallic cobalt hydroxide and4times higher than that of LDH powder prepared by a co-precipitation method. The high catalytic activity is attributed to the highly sufficient exposure of accessible active sites on the vertically-grown2D nanosheets. This study provides an alternative way for preparing high performance electrocatalysts based on LDH nanosheets, which are suitable for engineered applications owing to its robust binding and integrated construction onto metal substrates of arbitrary shapes. The current method is also applicable to the synthesis of CoFe-LDH film.