Synthesis Of Fe-Co-based Composites Based On Metal-organic Framework (MOFs) And Their Electrocatalytic Hydrogen Production

With the development of science and technology and national economy,the consumption of energy and resources is increasing day by day.Fossil energy reserves are limited and pollution is serious,and clean and pollution-free new energy sources are urgently needed for replacement.Meanwhile,according to the goal of achieving carbon neutrality by 2060,it is necessary to continuously promote the development of the new energy industry.Hydrogen energy uses hydrogen as the carrier,has high combustion heat,is clean and pollution-free,and is one of the popular clean energy sources.Hydrogen production from water electrolysis is considered to be the most likely efficient way to achieve large-scale green hydrogen production,and by converting electrical energy into hydrogen energy,excess power can be regulated across space and time.At present,large-scale commercial electrocatalytic materials are mainly Pt and Ir/Ru series noble metals,and the production cost is very expensive.Finding new electrocatalytic materials with low price,excellent performance and stable structure is the focus of research.Meanwhile,bifunctional electrocatalytic materials can greatly reduce the cost,which is a research hotspot.Metal-organic frameworks（MOFs）have the advantages of large specific surface area,abundant metal active sites,and stable structure,and can be used as excellent precursors for the synthesis of new electrocatalytic materials.In this paper,ZIF-67 was used as template and precursor,and it was modified by various means to prepare composite electrocatalytic materials with excellent performance.Water related properties.The main research work of this paper is as follows:（1）Co（NO₃）₂·6H₂O and FeSO₄·7H₂O were used as metal ion sources,and2-methylimidazole（2-MI）was used as organic ligand.At room temperature,by adjusting the ratio of metal salts,bimetallic FeCo@ZIF-67/NF composites with different ratios were prepared in situ on cleaned NF substrates.NF carries out the relevant structural and elemental characterization.FeCoC/NF electrocatalytic materials with different ratios were prepared by high temperature sintering in a tube furnace in an argon atmosphere,and their structure characterization and electrochemical performance tests were carried out.Among them,the overpotentials of HER and OER reactions of FeCoC/NF（1:10）at a current density of 10 m A·cm^-2are 240 m V and 338 m V,respectively,which are greatly improved compared with CoC/NF,and the bimetallic synergy can effectively It is a promising precursor material to enhance electrocatalytic activity.（2）FeCo@ZIF-67/NF（1:10）was used as the precursor for the reaction,and thioacetamide（TAA）and Na H₂PO₂·H₂O were used as sulfur and phosphorus sources for heteroatom doping,respectively.The sulfidation and phosphating processes were completed by hydrothermal method and low-temperature phosphating,and FeCoS/NF（1:10）,FeCoP/NF（1:10）and FeCoS@FeCoP/NF（1:10）electrocatalytic materials were prepared,respectively.Among them,FeCoS@FeCoP/NF（1:10）has excellent electrocatalytic performance,the HER reaction produces a current density of10 m A·cm^-2,the overpotential is 197 m V,and the OER reaction produces a current density of 20 m A·cm^-2,the overpotential is 295 m V.FeCoS@FeCoP/NF（1:10）was used as both cathode and anode,and the total hydrolysis test was carried out.Under the voltage of 1.565 V,a current density of 10 m A·cm^-2was generated,and the total hydrolysis performance was excellent.The stability test was carried out by the constant voltage current method,and the current did not decay significantly,and it had a good electrochemical stability.The experimental results show that the strategy of combining partial sulfidation and partial phosphating can effectively enhance the catalytic activity of electrocatalytic materials.（3）Using FeCo@ZIF-67/NF（1:10）as a precursor,complete ion exchange in Ru Cl₃aqueous solution,and then use Na₂HPO₄·H₂O as phosphorus source to perform low-temperature phosphating to prepare Ru-FeCoP/NF（1:10）Electrocatalytic materials.Ru-FeCoP/NF（1:10）exhibits excellent electrocatalytic performance:in 1 M KOH solution,the HER reaction generates a current density of 10 m A·cm^-2,only an overpotential of 95 m V is required,and the OER reaction generates 50 m A·cm^-2current density requires only an overpotential of 289 m V.The total hydrolysis reaction of Ru-FeCoP/NF（1:10）,the current density of 10 m A·cm^-2,the required voltage is 1.5 V.Moreover,the instantaneous current was measured under constant voltage for 10 h,the current was relatively stable,and there was no severe decay,and Ru-FeCoP/NF（1:10）had good electrochemical stability.The doping of a small amount of ruthenium element can enrich the electrocatalytic active sites and increase the electrocatalytic activity specific surface area.Ru-FeCoP/NF（1:10）electrocatalytic material has the potential for large-scale application.