The Oxygen Catalytic Performance Research Of Nickel/iron Hydroxide And Its Composite Materials

The oxygen evolution reaction(OER)is an important reaction of water decomposition and rechargeable batteries,causing people to pay more attention to the clean energy and high efficient energy store.There are two common strategy to improve the electrochemical performance of OER catalysts,including finding new catalytic materials and optimizing the chemical composition and structure of the existing materials.However,the energy efficiency of water decomposition is unsatisfactory mainly due to the slow kinetics of OER reaction.Therefore,it is urgent to find an efficient and stable catalyst which can reduce the overpotential and accelerate the OER reaction.The catalyst first applied in OER was RuO2 and other precious metals,but its application was limited due to the high price.Hence,we will need to find a catalyst that was abundant and high-performance.These demands mentioned before will continue to be the serious challenges in the future.Nickel / Iron based compounds are one of the most promising catalytic materials,which exhibit high catalytic activity in non-noble metal based catalysts.In this paper,we aim to provide a simple and efficient preparation method to prepare Ni / Fe double hydroxide and its composites.At the same time,the morphology and composition of these materials were characterized and the electrochemical performance of oxygen electrode catalyst was discussed,the main contents are as follows:1.Optimization of the synthesis strategy of double hydroxides nanosheets,with iron nitrate / nickel solution as raw material,and the direct use of sodium borohydride,which can obtain the nano iron / nickel metal nanoparticles,further reaction to get the target product.At the same time,this method can control the proportion of mother solution,so as to obtain the double hydroxides of different Fe / Ni ratio.In addition,due to the doping of Fe element,the prepared Fe / Ni bimetallic nanoparticles exhibit excellent electrochemical performance.Especially for Ni6Fe4-LDH,when the current density is 20mA/cm2,the oxygen evolution overpotential is only 0.24 V.2.We propose a method for efficiently preparing NiFe-LDH/ carbonnanotube composite material.Using carbon nanotubes as substrate,regulation of mother liquor concentration,make LDH uniformly grown on the substrate.This can not only effectively regulate the shape of LDH nanosheets,but also improve the catalytic stability of the catalyst.Compared to the pure NiFe-LDH sheet material,the stability can be doubled.Compared with the traditional synthetic route,this method is simple and efficient,and it can provide a certain reference value for mass production.3.On the basis of chapter one and two,the Fe-Co-Ni three metal hydroxide nanosheets were prepared by the same method.This method is mild condition and environmental friendly.Meanwhile,the strategy can effectively control the metal ratio in the synthesis of ternary hydroxide nanosheets,which provides a basis for the preperation of other single or composite transition metal hydroxide,which has certain universality.At the same time,in a series of ternary hydroxide,Fe4Co4Ni2-LDH displays the lowest overpotential of 0.273 V and 0.282 V,corresponding to the current density of 10mA/cm2 and 20mA/cm2,respectively.