Synthesis Of 2-mercaptopyrimidine-MOFs As Electrocatalysts And Electrocatalytic Properties For Water Splitting

Nowadays,with the excessive consumption of fossil fuels and the increasing environmental pollution,there is an urgent need to develop clean and renewable energy as a substitute.As a sustainable energy source with high energy density and non-pollution,hydrogen energy is considered as an ideal substitute for fossil fuels.Pure oxygen is also widely used in industrial and medical fields as combustion-supporting agent and respirable gas.Water electrolysis,as a clean and efficient technology for hydrogen and oxygen production,has attracted widespread attention.However,the hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）of water electrolysis need to overcome a large energy barrier,and the addition of an electric catalyst is needed to reduce the potential barrier and improve the reaction efficiency.At present,commercial electrocatalysts are mainly based on Pt/C,RuO₂and Ir O₂.However,their wide application is limited due to their low reserves and high cost.Therefore,it is urgent to develop electrocatalysts with rich sources,low price and high catalytic performance to replace precious metal based catalysts.Metal-organic frameworks（MOFs）,as porous crystalline materials with organic and inorganic hybridization,have been used in the field of catalysis.In the field of electrocatalysis,MOFs can be directly used as electrocatalysts due to their inherent framework structure and active ingredients.Due to poor electrical conductivity and strong acid or alkali resistance of pure MOFs,their direct application as electrocatalysts is still limited.It is significant to use 2-mercaptopyrimidine（Pym S）with both N and S potential active sites as an organic ligand and cheap transition metal to synthesize MOFs and further apply it forelectrocatalytic decomposition of water,which has both N and S potential active sites.This thesis based on Pym S has carried out the following research work:（1）A two-dimensional Ni-heteroatom based MOF array directly grown on carbon paper（Ni-MOF-A/CP）using 2-mercaptopyrimidine and nickel acetate tetrahydrate via one-pot solvothermal reaction.According to the strategy for MOF self-assembly on CP,Ni-MOFs also were synthesized on Ni foam（Ni-MOF/NF）with different sizes and morphologies.The newly resulting MOFs with ternary（Ni,S and N）active sites exhibited enhancing activity toward OER.In 1 M KOH electrolyte,The Ni-MOF-A/CP produced a low overpotential of333 m V at the current density of 5 mA cm^-2with a relatively small Tafel slope of 80 m V dec^-1.At the same time,the Ni-MOF/NF produced an extremely low overpotential of 302 m V at the current density of 10 mA cm^-2.In addition,the Ni-Mo F-A/CP could show at least long-term durability of 6 h.（2）A Pym S-Co was synthesized through solvothermal reaction with2-mercaptopyrimidine and cobalt chloride hexahydrate.whereafter,the catalyst of Ni@Pym S-Co was obtained via doping Ni²⁺into Pym S-Co.In 1 M KOH electrolyte,The Ni@Pym S-Co catalyst exhibited an extremely low overpotential of 350 m V at a current density of 10 mA cm^-2and a very small Tafel slope of 61 m V dec-1 for OER.Meanwhile,the Ni@Pym S-Co catalyst manifested excellent HER activity with a small overpotential of 349m V at 10 mA cm^-2and a low Tafel slope of 52 m V dec^-1.（3）A Pym S-Mn was synthesized through solvothermal reaction with 2-mercaptopyrimidine and manganese chloride tetrahydrate.Subsequently,the catalyst of Co@Pym S-Mn was obtained by doping Co²⁺into Pym S-Mn.In 1 M KOH electrolyte,The Co@Pym S-Mn catalyst exhibited an extremely low overpotential of 392 m V at a current density of 10 mA cm^-2and a very small Tafel slope of 53m V dec^-1for OER.