Regulation And Electrochemical Performance Of Two-dimensional Co/Ni Based(Hydroxide) Oxide Nanosheets

The rapid development of industry has led to a lack of energy,and water splitting as a promising way to provided clean and sustainable energy source of hydrogen and oxygen.Seeking high-performance electrocatalysts is the targets of current research for water splitting.The traditional oxygen evolution reaction（OER）catalysts are precious metals such as Pt and Ru and their derivatives,but the scarcity and premium price limiting their widespread application.Search for high-efficiency electrocatalysts and non-noble are the targets of current research.Supercapacitor is a kind of energy storage device,which has been attracted great attention due to their rapid charge and discharge,high energy density,high specific capacitance and excellent electrochemical stability anddurability.Two-dimensional Co/Ni-based hydroxides,due to their unique two-dimensional（2D）layered structure and high surface energy properties,have been used in many fields of electrocatalysis,supercapacitors,photocatalysis,and so on.Research of two-dimensional Co/Ni-based hydrogen oxide nanosheets are great significanc.Two-dimensional nanosheets of Al_0.2Co_0.8（OH）₂,Fe_0.2Co_0.8（OH）₂,Zn_0.2Co_0.8（OH）₂,Mn_0.11Ni_0.89（OH）₂ and Fe_0.11Co_0.44Ni_0.44（OH）₂ were prepared by hydrothermal method.The characterizations show that the addition of foreign ions changed the morphology,size and crystal structure of cobalt hydroxide and nickel hydroxide.Thus the specific surface area and the conductivity are increased.Electrochemical performance tests demonstrate that small amount of ion doping has a synergistic effect on cobalt hydroxide and nickel hydroxide.As electrode materials for supercapacitors,the specific capacitances of Al_0.2Co_0.8（OH）₂,Fe_0.2Co_0.8（OH）₂,Zn_0.2Co_0.8（OH）₂,Mn_0.11Ni_0.89（OH）₂and Fe_0.11Co_0.44Ni_0.44（OH）₂ were 709.1,736.02,638.13,1651.1,and 1155.47F/g at the current density of 1 A/g,respectively.For OER of water splitting,the overpotentials of the two-dimensional nanosheets of Al_0.2Co_0.8（OH）₂,Fe_0.2Co_0.8（OH）₂,Fe_0.11Co_0.44Ni_0.44（OH）₂were 348,282 and258 mV,respectively,at current density of 10 mA/cm².Tafel slopes were148,98.67 and 217 dec^-1,respectively.Compared to pure cobalt hydroxide（nickel hydroxide）,the electrochemical properties of two-dimensional nanosheets Al_0.25Co_0.75（OH）₂,Fe_0.25Co_0.75（OH）₂,Zn_0.2Co_0.8（OH）₂,Mn_0.11Ni_0.89（OH）₂ and Fe_0.11Co_0.44Ni_0.44（OH）₂ have been improved.Fe_0.2Co_0.8（OH）₂@PANI composites were prepared by hydrothermally treated Fe_0.2Co_0.8（OH）₂ on polyaniline.Using polyaniline as a based material not only improves the electrical conductivity but also increases the active area.For OER of water splitting,the overpotentials before and after the load were 282 and 261 mV,at current density of 10mA/cm².The Tafel slopes were 98.67 and 67.85 dec^-1.The results demonstrate that the addition of polyaniline improves the electrocatalytic activity.Al_0.33Co_0.67P was prepared by heat treated of Al_0.33Co_0.67（OH）₂.For OER of water splitting,the overpotentials of Al_0.33Co_0.67（OH）₂ and Al_0.33Co_0.67P were 483 mV and 328 mV,at current density of 10 mA/cm²,.The tafel slope of Al_0.33Co_0.67P is 109.72 dec^-1,which is smaller than that of Al_0.33Co_0.67（OH）₂(274.67 dec^-1).After the loading of P,the performance of electrocatalytic oxidation of water has greatly improved.