| 摘要 |
A process for applying an electrode of a catalytically active metal to an ion-exchange membrane comprises electrolytically depositing a thin layer of catalytically active noble metal on to an electrically conducting base e.g. of stainless steel, washing the deposit to remove the residue of the deposition bath, drying the washed electro-deposited catalytic metal, placing an ion-exchange membrane in contact with said electro-deposited metal, applying heat and pressure to the assembly to bond the catalytically active metal to the ion exchange membrane, and removing the ion exchange membrane, with the layer of electro-deposited metal attached, from the conducting base. The catalytically active metal may be applied in the form of an alloy with a non-catalytic material which is removed by etching prior to the application of the ion-exchange membrane. Specified catalytically active metals are platinum, palladium, indium, rhodium and ruthenium. In examples, Pt black is electro-deposited from an aqueous solution of chloroplatinic acid containing a small amount of lead acetate; Pd is deposited from a chloride solution, as also is an Pd-Ir alloy; a Pt-Rh alloy is deposited from a heated solution of the chlorides containing also NaNO2 and to which ammonia is added; while a deposit of Pt black is obtained by electro-depositing a Pt-Ag alloy from a bath containing chloroplatinic acid, silver chloride, lithium chloride, and hydrochloric acid and removing the silver by dipping the plated base in nitric acid. Specified membranes are made from sulphonated styrene polymers and a mixture of polyvinylidene fluoride and polytrifluorochloroethylene which may be swollen prior to contact with the noble metal coating, copolymers of styrene and vinyl benzene, zirconia and calcin-doped zirconia. Additional quantities of the noble metals or of different metals may be coated on to the outer surface of the first coating. Expanded metal screens formed of Pt, Ta, Au, or Ti containing 2% Pd or a layer of Au powder bonded with PTFE may be placed against or bonded to the noble metal as current collectors. The assemblies may be used in gas purification cells in which gas e.g. hydrogen supplied to one electrode is transported via the electrolyte and released at the opposite electrode. |
