Study On The Application Of Conjugated Organic Porous Polymers To Electrochemical Hydrogen Evolution

Hydrogen is a clean fuel with high energy density,and is the raw material of H₂fuel cell which is the main power of fuel cell vehicle in rapid development.Hydrogen energy industry is being developed by various countries.Comparing to other hydrogen production technology,the process of water electrolysis can directly use the electric power from photovoltaic and wind power,and has a broad application prospect.With the excellent electrochemical hydrogen evolution performance,platinum based noble metal catalysts are the most commonly used electrode catalytic materials.However,platinum is a scarce resource and high price limits its application.Development of an efficient and low cost catalyst for electrochemical hydrogen evolution become the key to large-scale production for water electrolysis process.At present,porous organic polymers,especially conjugated porous polymers with semiconducting properties,has attracted wide attention in the field of electrocatalytic hydrogen evolution,due to their both conductivity and porosity and having many advantages over traditional materials in catalysis.Based on this point,two conjugated organic porous polymers with different crystal structures,crystalline conjugated pore polymer a CQNs and amorphous conjugated microporous polymer m CQNs,were designed,prepared and characterized,and their electrocatalytic hydrogen evolution performance were tested.A molybdenum sulfide doped porous organic polymer material m CQNs/Mo S₂was further prepared to improve electrocatalytic performance of m CQNs.1.Covalent organic frameworks aCQNs was prepared using 2.5-diaminophthalo-nitrile as the raw material and zinc chloride as the catalyst.The effect of the molar ratio of zinc chloride to 2.5-diaminophthalonitrile on the crystal structure of a CQNs was investigated and the results show that a CQNs crystals have the highest quality under the molar ratio of 1.5.The results of characterization show that a CQNs polymer has a two-dimensional layered structure,and is formed by the orderly stacking of these sheet structures.The results of electrochemical hydrogen evolution test show that the overpotential is 80 m V under the current density of 10 m A·cm^-2,Tafel slope is 40mV·dec^-1,the exchange current density is 0.44 m A·cm^-2,and the double-layer capacitor(C_dⅡ)value is 0.40 m F·cm^-2.a CQNs polymer shows good catalytic performance and good electrochemical stability.2.Amorphous conjugated microporous polymer mCQNs was firstly prepared from m CQN monomer with Scholl reaction.m CQN monomer was prepared in advance at different temperatures using anthranilic benzonitrile as the raw material and zinc chloride as a catalyst.The results of of characterization show that m CQNs polymer has the disordered three-dimensional topological structure.The results of electrochemical hydrogen evolution test show that the overpotential is 170m V under the current density is10m A cm^-2,Tafel slope is 86 m V·dec^-1,the exchange current density is 0.33 m A·cm^-2,and the double-layer capacitance（Cd_Ⅱ）value is 0.23 m F·cm^-2.mCQNs polymer gives poor catalytic performance,but has good electrochemical stability.3.Molybdenum sulfide doped porous organic polymer,mCQNs/MoS₂,was synthesized with in situ growth method with m CQNs as the base,urea sulfide as sulfur source,ammonium molybdate as molybdenum source,in order to improving electrochemical hydrogen evolution performance of m CQNs.The results show that higher catalytic activity was given at m CQNs/Mo S₂2:1.The results of electrochemical hydrogen evolution test show that the overpotential is only 57 m V at the current density reaches is10 m A·cm^-2under acidic conditions,Tafel slope is 38 m V·dec^-1,and the double-layer capacitance（Cd_Ⅱ）value is 4.5 m F·cm^-2.m CQNs/MoS₂shows excellent catalytic performance and good electrochemical stability.