The Preparation And Catalytic Properties By Oxygen Reduction Reaction Of MOF Derivatives And Platinum-Based Composites

Fuel cell is a new kind of energy conversion device which is clean and efficient,with the slow kinetic process of oxygen reduction reaction(ORR)in cathode that needs to be catalyzed.Due to the scarcity and high cost of platinum,commercial Pt/C catalyst needs to be replaced by new electrocatalysts with the characteristic of cheap,steady and high catalytic activity.Thanks to the advantage of high specific surface area,hierarchical pore structure and homogeneous element dispersion,metal-organic frameworks(MOFs)derivatives are regarded as prospective catalyst for ORR.Herein,manganese based MOFs were prepared by coordinating with different ligands and metal,and its derivates served as catalyst or catalyst support for ORR.The main content is summarized as follows:(1)With manganese acetate and terephthalic acid as reactants,MnxOy/C,the micron scale spindle shaped derivative with optimal catalytic activity for ORR was obtained through the optimization of reaction time and calcination temperature,which shows good catalytic activity(onset potential is 0.883 V vs.RHE),superior durability and excellent tolerance of methanol.Whereafter,the product activated by melamine has smaller Tafel slope(111 mV dec-1)than before,closer to commercial Pt/C(107 mV dec-1),exhibiting better catalytic activity and the same four-electron mechanism.(2)With manganese acetate,zinc acetate and benzenetricarboxylic acid as reactants,the smaller nano-sized MOFs(Zn/Mn-BTC)were prepared by hydrothermal method,whose derivates has more micro-porous because of the autonomous removal of zinc during the calcinations process.The nanorods-like material ZMC obtained by optimization in bimetals ratio and reaction time exerts better catalytic performance than the above monometallic material,with the onset potential 0.896 V,superior long-term stability(the retention rate of current is 90.5%after 3 hours)and brilliant tolerance of methanol.(3)Taking the porous carbon(ZM-M)derived from Zn/Mn-BTC-MOF as support,the Pt/ZM-M catalyst prepared by polyols reduction method exhibits preferable catalytic activity and larger electrochemical active area than those composites loading on normal carbon support,even equivalent to commercial Pt/C.The galvanostatic charge and discharge test demonstrates that there are both double layer capacitance and ORR working during the discharge process,therefore the discharge specific capacitance of Pt/ZM-M in zinc-air battery is 13.3 times that of commercial Pt/C at the same current density of 100 A g-1.