Iron Electrodeposition And Its Application In Preparation Of Porous Materials

Porous materials are a kind of new materials,which have special properties of light of weight,large specific surface area,excellent electrical and thermal conductivity,have potential application in various area.Porous nickel,porous aluminum,and porous copper has already been widely used in electrochemical industry,aviation industry,and environmental protection,etc.Iron is cheap and has catalytic property,which reduce or replace the usage of more expensive Nickel in certain occasions,the development of porous iron has a potential value.The preparation methods of porous materials include solid phase method,liquid phase method and electrodeposition method.Among them,the electrodeposition method has the advantages of short operation process,low energy consumption,and less environmental pollution,and has rapidly extended in manufacture field in recent years.However,the common electrodeposited iron bath has many problems such as easily be oxidation,serious hydrogen evolution resulting low current efficiency,and poor throwing power,which is not appropriate for the preparation of porous iron.In this thesis,the parameters of electrodeposition and the bath formula are systematically studied and optimized before the preparation of porous iron.The effects of plating temperature,pH of bath,current density and ferrous chloride concentration on cathode current efficiency and micro-structure of the deposition layer are studied by Taguchi orthogonal experiment method.The effects of inorganic additives on the morphology,cathode current efficiency and throwing power of electrodeposited iron are studied by Hall Cell and Haring Cell electroplating experiments.The electrochemical behavior of organic additives on electrodeposited iron is studied by cyclic voltammetry and galvanostatic method.Finally,porous iron is prepared under the optimized conditions and bath solution formula.This study draws the following conclusions:(1)Bath pH is the most important factor among the various affecting parameters of the electrodeposited iron.The low pH results fast hydrogen evolution reaction,and form cracks and pitting points in the deposited layer.When the pH is too high,the iron hydroxide co-deposited with iron,which increases the brittleness of the iron layer.Current density affects the deposition rate on the cathode.When the current density is higher,it generates burnt and coarse deposition.When current density is lower,the cathode current efficiency decreases.Temperature affects the rate of ion migration and reaction rate.Ferrous ion concentration has minor effect on the plating and cathode current efficiency.(2)The additives significantly affect the cathodic electrodeposition process and change the microstructure of iron deposition layer.The addition of manganese chloride improves the cathode current efficiency.Ascorbic acid,an antioxidant can inhibit the oxidation of ferrous ions and stabilize the bath.Ammonium citrate is added into the solution as the pH buffer,it makes the deposition dense and uniform at the same time.Through the comparison of the electrochemical effect of sodium saccharin,thiourea,urea and PEG-8000,thiourea significantly inhibits hydrogen evolution and improves cathode current efficiency.The addition of thiourea rises cathode current efficiency up to 85%,and obtains dense,flat coating layer.(3)By optimizing electroplating parameters and bath formula,the bath solution of electrodeposited iron consists of manganese chloride 20 g/L;ferrous chloride 300 g/L;ammonium citrate 40 g/L;ascorbic acid 1 g/L;thiourea 20 mg/L.The porous iron is prepared from this optimized electroplating formula,its specific surface area is 0.7994m~2/g.