Research And Application Of Two-Dimensional Conductive MOF Based On HITP Ligands For Photo/Electrocatalysis

Metal-organic frameworks(MOFs)are a class of metal-organic composites with pore structure,high specific surface area,and flexible structure.They have been studied for countless applications,especially in gas separation and storage,sensing,and photoelectrocatalysis.With the increase in energy demand in recent years,devices such as fuel cells,supercapacitors,thermoelectrics,and resistance sensing have been extensively studied.Due to the above characteristics,MOFs have been continuously developed.However,low electrical conductivity limits their utility in many of the required technologies.Therefore,the development of new MOF materials with higher conductivity is an important research direction to realize the functionalization of MOF in the energy field.Based on the ligand of hexaaminotriphenylene(HITP),two kinds of conductive MOF materials,Ni3HITP2 and Co3HITP2,were synthesized.The photocatalytic properties of photocatalytic reduction of CO2 and electrochemical oxygen evolution(OER)and oxygen were studied.Electrocatalytic performance such as reduction(ORR).The main work carried out in this paper is as follows:1.Metal-organic frameworks(MOFs),as a new class of porous materials,combine CO2 capture and catalytic conversion for C02 reduction in photocatalytic systems.However,the lack of structural stability in conventional MOFs,conductivity and electron trap states hinder stable and efficient charge transport and transfer during photocatalytic cycling expose a problem that needs to be overcome.In this experiment,we synthesized Ni3HITP2 two-dimensional nanosheets with high conductivity(5000 S· m-1)and explored its potential for photocatalytic reduction of CO2 in visible light photocatalytic systems.By using conductive MOF nanosheets as cocatalysts,the hybrid photocatalytic system showed high CO yield.It was 3.45 × 104 ?mol·g-1 h-1 and had a high selectivity of 97%in 3 hours.No decay of the MOF catalyst was observed in a total of 6 repeated catalytic cycles,showing excellent stability,high electrical conductivity,rich Ni-N4 active sites and Ni3HITP2 2D nanosheet morphology,which achieved excellent photocatalytic performance.2.Electrocatalytic oxygen reduction(ORR)and oxygen evolution(OER)are very important in the field of electrochemistry,which is the half-cell reaction in regenerative fuel cells and rechargeable metal air cells.At present,platinum group metals(PGM)are widely used in the industrial field as a kind of electrocatalyst with high catalytic performance.However,due to the expensive price of Pt,lower reserves,and their instability during the catalytic process,it is important to develop low cost and earth-rich electrocatalysts with catalytic performance comparable to or superior to PGM.In this experiment,a series of MOF materials including Ni3HITP2,(Ni/Co)3HITP2 and Co3HITP2 were synthesized,and the ratio of metal in MOF was controlled by changing the ratio of nickel to cobalt during the synthesis process,so that different metals were used as catalytic active centers for electricity to study the effect of different metals as catalytic active centers during the electrocatalytic ORROER process.Among them,Co3HITP2 has an overpotential of 350 mV in the OER test at a current of 10 mA·cm-2,and a half-wave potential E1/2 of 0.76 V in the ORR test,showing good bifunctional electrocatalytic performance.3.On the basis of the second part,we introduced the foam nickel substrate to improve the current collection efficiency in the electrocatalytic process and improve the synthesis method of Co3HITP2,which is applied to the cathode end of the zinc-air battery.This experiment was carried out by growing a-Co(OH)2 on the foam and then converting it in situ to the MOF material of Co3HITP2.The catalyst has a high specific surface area,good electrical conductivity and a porous structure.At a charge and discharge current density of 10 mA·cm-2,a zinc-air battery based on Co3HITP2/NF is at a lower charge/discharge overpotential.It has been cycled for more than 200 hours and exhibits superior electrocatalytic performance and catalytic stability beyond the commercial Pt+RuO2 catalyst.