Experimental Study On Interface Impedance And Surface Treatment Of Porous Transport Layers In PEMEC

Proton exchange membrane electrolysis cell（PEMEC）can electrolyzes water to produce hydrogen through electricity.The product is only hydrogen and oxygen.It has the advantages of high environmental protection,high working current density,high hydrogen production pressure and fast dynamic response.In addition,it can be combined with wind energy,solar energy or other volatile sustainable energy which has great development potential and is unstable in output.It has great development potential and broad application prospect.Titanium is widely used as anode material in PEMEC due to its excellent corrosion resistance.However,using titanium material will seriously reduce the electrolytic performance.And in electrochemical impedance spectrum,it shows a high frequency impedance arc with capacitive property.Therefore,it is necessary to systematically explore the performance of PEMEC and optimize the surface of titanium materials.In this paper,there is a reaction area of 25cm² in PEMEC and a test platform was built.The influences of anode plate’s material,PTL’s material and structure,assembly torque,working temperature and flow rate on the overall performance and internal impedance of PEMEC were investigated.The key factors that reduce electrolytic performance of titanium are analyzed.What’s more,a variety of surface optimization schemes were designed for the treatment of titanium mesh or titanium felt by Adams fusion.The scanning electron microscopy,polarization curves and EIS were compared to analyze the effect of impedance on performance.The effect of different materials on the performance of electrolytic cell was compared.The results show that titanium produces high frequency impedance arcs with capacitive properties in electrochemical impedance spectrum and leads to serious degradation of electrolytic performance.The high frequency impedance arcs may be caused by the poor charge conductivity of titanium surface or its ion adsorption after electrolysis.As the current density increases,the potential increases and the interfacial impedance decreases.As the assembly torque increases,the ohmic impedance of PEMEC is almost unchanged,while the interfacial impedance of titanium plate,titanium mesh or titanium felt all increase.The influence of temperature and flow rate on PEMEC was also investigated.As working temperature increases,the ohmic impedance,activation impedance,concentration impedance and interface impedance decrease,while the interface impedance of titanium felt shows an upward trend because the oxidation rate of titanium felt will accelerate rapidly above 70℃.As the flow rate increases,the concentration impedance decreases.And the variation trend of titanium felt’s concentration impedance is much more signification than that of titanium mesh.In order to reduce the interface impedance,the surface optimization of titanium mesh and felt is carried out by Adams fusion.The influence of adding the powder of Na NO₃ on PEMEC was investigated.The powder of Na NO3 weakens the optimization of interface impedance and increases the concentration impedance.Moreover,titanium mesh’s mesh structure and bending state make it more difficult for coating treatment.The coating material distribution on the wire surface is not uniform.After surface optimization treatment,the electrolytic voltage of titanium mesh is reduced by 74 m V at 1.0 A cm^-2.However,the titanium felt’s fiber structure and smooth state make it easy for coating treatment.The coating material distribution on the fiber surface is evenly uniform.After surface optimization treatment,The electrolytic voltage of titanium felt is reduced by 501 m V at 1.0 A cm^-2.