Construction And Electrochemical Water Splitting Performance Of Fe-Co(Ni)-P Multi-Heterostructure Catalysts

In recent years,in order to achieve sustainable development,human societies have paid more and more attention to the energy and environment protection.It is essential to build a low-carbon and efficient energy supply system in an all-round way and use green and clean non-fossil energy in a large scale to achieve sustainable development.Hydrogen energy,as one of the cleanest energy,has attracted extensive attention from researchers and government departments.Electrocatalytic hydrogen evolution,as a highly efficient technology for hydrogen production,has long been plagued by high cost noble metal catalysts.However,it is difficult to be applied commercially on a large scale.In order to reduce the cost of electrocatalytic hydrogen evolution,it is urgent to explore new catalysts with lower cost to replace noble metal catalysts.Based on previous studies,transition metal phosphide has a good potential for electrocatalytic hydrogen evolution.Meanwhile,recent studies have also shown that the electronic structure of the catalyst can be effectively regulated by the construction of heterogeneous structure,and a synergistic effect can be generated to improve the catalytic performance.In conclusion,reasonable selection of precursor materials and construction of heterogeneous catalysts may have excellent electrocatalytic performance of full water splitting.The main research work of this thesis is as follows:1.Basic cobalt carbonate（Co CH）with array morphology was selected as the self-sacrifice template,and the Co source was used to react with potassium ferricyanide.Then the Co-Fe PBA is in situ grown on the self-sacrifice template.Finally,the precursors are transformed into Fe-Co-P heterogeneous catalysts by a low temperature phosphating method.The catalyst has excellent HER/OER catalytic performance,requiring only 227 and 87 m V to reach current densities of 20 and 10 m A cm^-2,respectively,for OER and HER,in the absence of precious metals.More importantly,it has better performance than commercial catalysts when used to drive fully dissolved water in alkaline electrolytic cells,which provides a current density of 10 m A cm^-2 at1.55 V,and a nearly 100%Faraday efficiency.By combining DFT calculation and characterization,we confirm the formation of multiple heterostructures and reveal the intrinsic reasons for the excellent performance of the catalysts.The formation of Fe-Co-P heterostructure can adjust the local electronic states of the materials,and optimize the adsorption and desorption of the catalytic reaction intermediates,thus reducing the reaction barrier,and greatly enhancing the activity of Fe-Co-P/NF catalyst.At the same time,the unique open structure of catalyst provides a larger active area and exposes more active sites.2.The extensibility of self-sacrificing template synthetic route of heterogeneous catalysts is verified by changing the types of precursors.The precursor Ni LDH with"nanoflower"structure is selected as self-sacrifice template,and Fe-Ni PBA is synthesized using potassium ferricyanide as iron source.The same low temperature phosphating method is used to convert the precursor into Fe-Ni-P heterogeneous catalyst.The prepared Fe-Ni-P/NF catalyst also has excellent HER/OER catalytic performance.The heterogeneous structure is confirmed by structural characterization and electrochemical testing,and improves the catalytic reaction kinetics,thus increasing the catalytic activity of the catalyst.More importantly,the morphology of the prepared catalyst inherits the original morphology of the template to a large extent,confirming that the self-sacrificing template can play an important role in limiting the growth and avoiding the accumulation of catalysts.This synthetic route provides a new idea for reasonably regulating the morphology of catalysts and constructing new electrocatalytic catalysts for full water splitting.