The Study On Preparation And Performance Of Foam Palladium Catalyst For Pb-C Battery Eliminating Hydrogen

Pb-C battery is a good choice for Hybrid-Electric Vehicle （HEV） because of its goodsecurity, low cost and long life at high rate partial state of charge （HRPSOC）. However,there is a serious problem of hydrogen releasing which would lead failure of thebattery by water loss. Because carbon was taken in negative electrode. It is veryimportant to reduce water loss by catalyst and enhance performance.In this study, preparation process of foam carbon was optimized firstly, and thenfoam Hydrogen-elimination catalyzer, a layer of Pd, was plated by the methods ofelectroless plating and electroplating. The activity of foam catalyzer was measured inthe test apparatus. The scanning electron microscopy（SEM）, XRD, electrochemicaltesting and other means were taken to analyze factors affecting catalytic activity.Preparation conditions were optimized as follows: After dipping with caustic sodaand alcohol, the foam was impregnated into furfuryl with9mass%addition agent,then was dried under the condition of120℃for1hour. The additive concentration ofthe second impregnating solution is5mass%. Finally carbon foam was obtained byHigh-temperature sintering. Special features of the carbon foam gotten under theoptimized processes are showed as follows: The specific surface area of carbon foam is1.35m²/g with an amorphous structure and it was almost no oxidation below500℃.The order of the reaction was tested at the room temperature. It was proved that thecatalytic reaction is0.5order in oxygen and0.5order in hydrogen when concentrationsof hydrogen and oxygen are3:1. It was showed that catalyzer prepared by electrolessplating had a higher activity than electroplating, the reaction rate per unit mass are0.67min^-1and0.53min^-1respectively, although the specific surface area of electrolessplating catalyzer larger40%than electroplating. The half-life period of catalystreaction decreases significantly with the load increasing of palladium, For example,reaction rate induced from0.009169min^-1to0.019748min^-1when palladium loadincrease from0.0069g to0.0203g, The catalyst activity increased obviously after-treatment, the test showed that after treatment the reaction rate rather than1.155min^-1.There is a dynamic equilibrium between bulk phase and the surface for hydrogen onthe palladium. Increasing the thickness of the palladium layer and after-treatmentcould enhance the concentration of hydrogen in the surface and then accelerate thereaction rate of H_ad+O_adâ†'OH_ad which is the rate determining step.