Preparation And Electrochemical Properties Of MOF-derived Carbon Paper Self-supporting Electrodes

There is a very urgent need to develop clean and renewable energy for the sustainable development of the society,which mainly focus on efficient energy conversion and improved energy storage for on-demand use.The electrolysis of water to produce high-purity hydrogen is an effective electrochemical conversion process that is used to store and utilize renewable energy.At present,in order to solve the slow kinetics,high overpotential and achieve efficient energy conversion,precious metal based catalysts including Pt/C and Ru/Ir O₂are considered to be high efficient electrocatalysts for HER and OER,respectively.However,the high price and scarcity of these materials limit their wide application.Supercapacitors are a subset of energy storage devices that are important because of their high power density,greater circulation capacity and affordability compared to similar products.Metal-organic framework（MOF）are classical porous materials,which have great potential applications in catalysis and energy storage.MOF is an ideal precursor or template for the production of catalytic and energy storage active materials for various reactions,and even some MOF can be directly applied in the electrochemical field.Their unique structure,high specific surface area and developed porosity are conducive to their application in the electrochemical field.Moreover,the size,shape,porosity and combination of MOF materials can be precisely adjusted.But MOF generally has poor electrical conductivity,combining MOF with carbon paper can provide a good conductive path and eliminate the need for binders.In this paper,a self-supporting MOF composite electrode is designed by combining MOF and carbon paper.The specific work is as follows:（1）Two growths of ZIF-L are carried out on carbon paper at room temperature.Co and Ni are introduced through two growths and a 3D hexagonal crossed flower-like ZIF-L（Co）@ZIF-L（Co,Ni）is obtained.The electrode（CN-2）/CP can be directly used as an electrode for testing.The prepared array electrode（CN-2/CP）shows good electrochemical activity and stability in both the oxygen evolution reaction and the supercapacitor.In the oxygen evolution reaction（OER）,the CN-2/CP electrode has an overpotential as low as 230m V when the current density is 10 m A cm^-2.In the 40-hour chronopotentiometric measurement,its catalytic stability is high,and the potential retention rate is as high as 91%.when employed in a supercapacitor,the CN-2/CP electrode delivers a high specific capacitance of 1346 F g^-1at 1 A g^-1,and an excellent cycle stability with a capacitance retention of 88.5%after 7000 charge/discharge cycles at 20 A g^-1.The high performance originates from the in-situ electrochemical conversion of metal hydroxide（Co-Ni LDH）,improved conductivity,fast electron charge transfer at interface between ZIF-L(Co@ZIF-L（Co,Ni）and Co-Ni LDH,and unique layered cross morphology providing more active sites.（2）Firstly,MIL-101（Fe）was grown in situ on carbon paper,and ZIF-L（Co）was grown again,using the MOF-on-MOF strategy to introduce bimetals.MOF is used as a precursor for low-temperature phosphating to obtain a self-supporting electrode material Fe P-Co P/CP.Electrochemical tests under alkaline conditions show that the material has good electrocatalytic activity for both HER and OER.It is worth noting that when used as a positive electrode and a negative electrode at the same time,a low potential of 1.62 V is required to achieve a current density of 10 m A cm^-2.Fe P-Co P/CP serves as an active dual-function electrocatalyst for overall water splitting.Its good electrocatalytic activity is due to the synergistic effect of bimetallic phosphide and its self-supporting properties.This work provides a simple and effective method for the design of self-supporting bimetallic phosphating catalysts.We have successfully grown MOF on carbon paper and designed a strategy of secondary growth of MOF.Not only can we obtain MOF/CP electrodes for direct electrochemical testing,but also MOF can be used as a precursor to obtain bimetallic phosphides.It has a good performance in the field of electrolytic water and super capacitors.