| Direct methanol fuel cell（DMFC）has attracted much attention because of its advantages such as rich fuel sources,high energy density,and pollution-free.However,the low activity and high polarization potential of anodic methanol oxidation seriously affect the energy conversion efficiency of DMFC.Therefore,it is essential to solve the critical problem of low anode reaction activity through the in-depth study of anode catalytic materials to promote the wide application of green energy in fuel cells.Nickel has specific catalytic methanol oxidation ability and anti-CO toxicity in an alkaline medium.The alloy can induce electron effect and bifunctional group mechanism,which can significantly improve the catalytic activity and stability of the material.In this paper,combined with the advantages of microfluidic technology,such as simplicity and efficiency,accurate control of reaction conditions,high mass and heat transfer,nickel-based composite nanoparticles with uniform particle size and good dispersion were synthesized in a microfluidic reactor and applied to the anodic methanol oxidation of DMFC.The details of the study and the results are as follows.（1）A miniature three-pass microfluidic reactor was built.By controlling the heating temperature,we formed a gas-liquid segmented flow in the microchannel to accelerate the reaction process and prevent channel blockage.The metal precursors were reduced to nucleus in the microreactor and grown into CuNi/C nanoparticles.In the microreactor,the metal precursors were reduced to nuclei and grown into CuNi/C nanoparticles.The effects of different conditions on the material morphology and electrocatalytic performance were investigated by varying the flow rate,surfactant,metal ion addition ratio,and reductant concentration.The materials’microscopic morphology,crystalline structure,and elemental valence state were characterized by TEM,XRD,and XPS.The electrochemical platform was used to test the electrocatalytic activity of the materials under different conditions.The experimental results showed that in an electrolyte of 1M KOH and 1 M methanol,the current density of CuNi/C materials prepared under the optimum reaction conditions reached 124.6 m A/cm~2（vs.Ag/Ag Cl）at 1 V,and excellent electrocatalytic stability within 4000 s.Under the same reactant conditions,the solvothermal method and microfluidic method were compared to investigate the effects of preparation methods on the morphology and catalytic properties of the materials.The results showed that the materials prepared by the solvent-heated method had low alloy ability and severe oxidation and agglomeration;the current density of CuNi/C materials under the microfluidic method at 1 V was much higher than that of the solvent-heated method.（2）CoNi/C nanomaterials were synthesized by the microfluidic method at 95℃.We investigated the effects of different conditions on the morphology and electrocatalytic properties of CoNi/C by varying the solvent system,flow rate,additives,metal ion addition ratio,and reductant concentration.The morphology and elemental composition of the materials were investigated by means of TEM,XRD,and XPS characterization,and the electrocatalytic properties of the materials were evaluated by the electrochemical platform.In the electrolyte of 1M KOH and 1 M methanol,the current density of CoNi/C material prepared under the optimal reaction conditions is 85.74 m A/cm~2（vs.Ag/Ag Cl）at 1 V.The electrocatalytic stability of the material is good within 4000 s.This paper successfully prepared CuNi/C and CoNi/C nanoparticles with a small average particle size and good dispersion by the microfluidic method.Both materials showed excellent catalytic activity for the methanol oxidation reaction.The microfluidic method improves the material morphology and electrocatalytic performance and reduces the preparation cost of catalyst.It broadens the application of microfluidic technology in the field of transition metal alloy catalyst. |
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