Preparation And Electrocatalytic Performance Of Several Nanostructured Electrodes

Nanomaterials are widely used in many fields such as electrocatalysis,fuel cells,biosensors,and photocatalysis due to their unique structures and properties.Numerous methods have been reported for the preparation of nanomaterials,and new methods are constantly emerging.Among them,the electrochemical method is usually used to prepare nanomaterials because it's environmentally friendly and easy to operate under mild conditions.In this thesis,several nanostructured materials were prepared by means of electrochemical method.The resulting materials were used in the electrocatalytic oxygen evolution reaction?OER?,electrocatalytic oxidation of ethanol,and electrocatalytic reduction of nitrate.The main content is as follows:1.A nanonickel-iron sulfide?NiFe-S/NF?nanosheet film was prepared by the combination of a cathodic potentiostatic deposition and a hydrothermal method for electrocatalytic oxygen evolution reaction.First,a rough NiFe layer was rapidly electrodeposited onto nickel-foam?NF?substrate?NiFe/NF electrode?at high cathodic potentials in a mixed solution containing ferric chloride and nickel chloride.After being cleaned,the NiFe/NF electrode was then placed in a reaction kettle containing a thiourea solution for hydrothermalreaction to obtain a NiFe-S/NF nanosheet film electrode.The effects of hydrothermal temperature,time,and thiourea concentration on the catalytic performance of the electrode were investigated.The Ni Fe-S/NF nanosheet film electrode has a low overpotential of 245mV for OER at a current density of 10 mA cm^-2 in alkaline solution and a good stability when running for 10 h.2.A NiFeOH-coated nickel-iron?NiFeOH-Ni Fe/NF?electrode was facilely prepared by cathodic electrodeposition followed by in situ chemical modification on a nickel foam substrate,and the obtained electrode was used for the electrocatalytic oxygen evolution.The NiFe/NF electrode prepared in part one was taken out from the precursor solution and directly put into the test solution of 1 M KOH without cleaning.The porous modified layer of NiFeOH thus in situ formed on the rough NiFe/NF surface through a precipitation reaction of precursor and KOH.The resulting NiFe OH-NiFe/NF electrocatalyst has a high activity,namely only a overpotential of 223mV at a current density of 10 mA cm^-2 and at least 10 h stability,toward the electrocatalytic splitting of water into oxygen.3.A dendritic nanoporous palladium film?DNPF?electrode with very high roughness was rapidly prepared by an anodic potential step within several minutes in a mixed solution of sodium hypophosphite and potassium chloride,involving anodic dissolution of Pd in KCland simultaneous chemical reduction of generated Pd salt by hypophosphite.Meanwhile,the in situ-released gas from the decomposition of hypophosphite can be used as a dynamic template,which benefits the formation of dendritic nanoporous structure.The resulting DNPF electrode showed high electrocatalytic activity toward the oxidation of ethanol and reduction of nitrate.The cyclic voltammetry results showed that the oxidation peak current density of the DNPF electrode for ethanol oxidation is 650.19 mA cm^-2,which is 42 times higher than that of the smooth Pd.As for reduction of nitrate,the reduction current density of the DNPF electrode at-1.5 V is 169.5 mA cm^-2,which is much larger than bright palladium(0.5mA cm^-2).The chronoamperometry results on the DNPF also showed good stability for electrocatalytic oxidation of ethanol and reduction of nitrate.