Study On Preparation And Properties Of Cobalt Film Electrodeposition On Platinum Surface

The study of underpotential deposition(UPD)of cobalt(Co)on platinum(Pt)mainly focuses on the single-crystal Pt matrix and acidic solution,while the study of UPD and over potential deposition(OPD)of Co on polycrystalline Pt matrix is rarely reported.Since most Pt is polycrystalline,the surface active sites of polycrystalline Pt are numerous and the energy states are discrete.Therefore,it is of great significance to study the electrodeposition behavior of Co on polycrystalline Pt.In this study,the optimal treatment method of Pt electrode surface was firstly explored.The UPD and OPD behaviors of Co on metal Pt surface were studied by cyclic voltammetry(CV),and the effects of different factors(Co ion concentration,reversal potential,scanning rate)on UPD and OPD behaviors of Co on metal Pt surface were analyzed.Co films were prepared by electrodeposition on metal Pt surface in different anionic plating systems,and the effects of different anionic ions on the structure and properties of Co films were investigated.At last,the electrocatalytic properties of Co film deposited under potential on metal Pt surface were analyzed.The main conclusions are as follows:(1)The treatment effects of three methods of burning,chemical polishing and electrochemical polishing on the surface of Pt piece electrodewere compared,and it was found that the treatment effect of electrochemical polishing was the best.(2)The deposition behavior of Co on the surface of metal Pt was studied by cyclic voltammetry.In the negative scanning process,peaks of A,B and C were observed at-0.120 V,-0.380 V and-0.840 V respectively(peak A was caused by the conductive salt in the solution,peak B was the UPD peak of Co on the polycrystalline Pt surface,and peak C was the OPD peak of Co on the polycrystalline Pt surface).When scanning in the forward direction,D,E and F peaks(D peak is the dissolution peak of the hydrogen-cobalt rich phase,E peak is the dissolution peak of the OPD peak of Co on the polycrystalline Pt surface,and F peak is the dissolution peak of the UPD peak of Co on the polycrystalline Pt surface)appeared at-0.710 v,-0.520 v and0.290 v respectively.(3)The structure and properties of Co films deposited on metal Pt surface in different anionic plating systems were studied.The results show that: the crystal peak of Co(220)is the strongest,the crystal grains of Co grow like needles and are evenly arranged,the coating surface is rough,the film is thick,and the corrosion resistance is the strongest.The crystal peak of Co(111)in sulfate bath system is the strongest,the grain of Co grows in a ball,the coating surface is flat,the film is thin,and the corrosion resistance is weak.The crystal peak of Co(111)was the strongest in the system of chloride ion plus citric acid plating solution.Due to the change of the preferred orientation of the growth of Co grain due to the addition of citric acid,the grain size of Co was small,the coating surface was smooth,the film was the thinnest,and the corrosion resistance was the worst.(4)The electrocatalytic performance of Co film deposited by under potential on metal Pt surface was studied.The minimum theoretical applied bias required for the deposition of Co film under potential on metal Pt surface in a photovoltaic hydrogen-producing system is obtained.When the applied bias is-1.0v,the conversion efficiency of solar energy to hydrogen energy(STH)can be obtained by 8.28%.