Preparation Of Spinel Oxide-based Nanocomposites And Their Electrocatalytic Oxygen Evolution Properties

At present,the energy crisis and environmental pollution are still major problems facing humankind in the 21 st century.One of the effective methods to solve these problem is to produce hydrogen by electrocatalytic water splitting.As we known,hydrogen is an ideal new energy source which can replace traditional fossil energy.Its only combustion product is water,which will not cause any pollution to the environment.Now,the biggest problem in hydrogen production by electrocatalytic water splitting is that the efficiency of electrocatalytic hydrogen production is not high and it is difficult to meet the application needs.The catalyst can accelerate the efficiency of electrocatalytic water splitting to produce hydrogen to a certain extent.The effective catalysts that can be used for electrocatalytic water splitting are mainly some noble metal-based catalysts（Pt,Ir O2 and Ru O2）.They can speed up the efficiency of water decomposition,but the high price severely limits their widespread applications,so it is urgently needed to develop inexpensive electrocatalysts with high efficiency.Herein,we synthesizedthe core-shell structured nanowire arrays as an OER electrocatalyst using a simple two-step method.The obtained nanocomposites are characterized by various methods and their OER electrocatalytic performances are evaluated.The specific research results are as follows:（1）We synthesized a CoFe-LDH/Ni Co₂O₄/Ni foam（CoFe-LDH/NCO/NF）core-shell nanowire array by a simple two-step method.The synthesized CoFe-LDH/NCO/NF shows excellent OER electrocatalytic activity and stability.The remarkable electrocatalytic performances of the CoFe-LDH/NCO/NF electrode ascribe to the strong synergistic effect between the Ni Co₂O₄（NCO）nanowires core and the CoFe-LDH nanosheets shell.In addition,the unique structure and composition of the 3D nanocomposites that have been prepared also help to enhance their OER performance.（2）We used foamed nickel with good conductivity as the supporting framework and prepared a NiFe-LDH/Mn Co₂O₄/Ni foam（NiFe-LDH/MCO/NF）core-shell nanocomposite by a two-step hydrothermal method.The synthesized nanocomposites exhibit excellent OER properties.The presence of high-valence Mn⁴⁺ in NiFe-LDH/MCO/NF helps to improve the catalytic performance of electrode materials.In addition,the direct growth of the active material on the nickel foam substrate avoids the use of adhesives,and the synergistic effect between the core and the shell of the nanocomposite material also contributes to the improvement of catalytic performance.