| Abstract:Hydrogen energy is a kind of clean renewable energy which has many prominent merits such as rich in resources and easy to store up. Because of the exhaustion of the fossil fuels and the environmental crisis, people have paid more attention to it. The main method to prepare hydrogen on a large scale is water electrolysis. In order to decrease cathode overpotential for reducing energy consumption, it’s of momentous significance to research new cathode eleetrode materials which have lower hydrogen-evolution overpotential and high catalytic activity. There are two important factors that can affect the catalytic activity of the hydrogen-evolution materials:energy factors and geometry factors. So there are two main methods can be taken to prepare cathode materials for hydrogen evolution which own high catalytic activity. One is to search for a new kind of catalytic materials of high catalytic activity so as to improve electrocatalytic activity of the electrode itself. The other is to inerease the actual specific surface area of the electrode, namely to amplify the electrode surface roughness which can decrease the true current density of the electrode surface in the course of electrolysis reaction so as to reduce the cathode overpotential. In this thesis, nanoporous nickel alloys composite electrodes were prepared by electrodeposition technique and characterized every electrode by SEM, EDS and XRD, and also analysised the electrochemical properties of hydrogen evolution reaction in25wt%KOH solution. The achievement will provide theoretic and technical support for water electrolysis with low energy, promote the development of the water electrolysis technique for hydrogen production. The main research contents are listed as following:1. Ni-W alloy coatings were prepared by electrodeposition technique in citric acid system. The influence of the main technical parameters on the compositions and surface quality of Ni-W alloy coatings were investigated, the bright Ni-W alloy coatings with W25.78wt%and Ni74.22wt%were obtained. The results showed that porous Ni-W alloy electrodes were obtained by removing templates electrodeposition methods, the inorganic templates were nano silica microspheres, the organic templates were nano polystyrene microspheres, the bubble templates were hydrogen bubbles. The methods of removing inorganic and organic templates electrodeposition for preparing porous Ni-W alloy electrodes were feasible, but the hydrogen evolution electrodes for electrolyzing water were ineffective. The electrodes with porous structure were obtained by bubble template electrodeposition method at high current density but the content of W in the Ni-W alloy coatings was too little, so it was difficult for obtaining porous Ni-W alloy electrodes using this method.2. Ni-Mo alloy coatings were prepared by electrodeposition technique in citric acid system. The influence of the main technical parameters on the compositions, surface morphology and the electrocatalytic activities for hydrogen evolution of Ni-Mo alloy coatings were investigated, the bright Ni-Mo alloy coatings with Mo35.51%wt%and Ni64.49wt%were obtained. Nano TiO2particles with average diameter510nm were prepared by Sol gel-surfactants. Nano hierarchically porous Ti-SiO2and Al-SiO2particles were prepared by using in-situ method. The diameter of Ti-SiO2particles were from200nm to500nm, specific surface area was573m2/g, pore volume was1.19cn3/g and mesopore size was3.2nm. The diameter of Ti-SiO2particles were from200nm to800nm, specific surface area was396m/g, pore volume was1.37cm/g and mesopore size was3.3nm. Nano hierarchically porous Ni-Mo composite electrodes were prepared with nano TiO2particles, nano hierarchically porous Ti-SiO2and Al-SiO2particles as composite particles respectively. The influence of the concentration of composite particles on the electrocatalytic activities of Ni-Mo composite electrodes for hydrogen evolution were investigated by polarization curves, the results showed that the electrocatalytic activities of Ni-Mo composite electrodes for hydrogen evolution reached the optimal values when the concentration of nano TiO2particles, nano hierarchically porous Ti-SiO2and Al-SiO2particles were4g/L2g/Land2g/L respectively. The influence of the three composite particles on the electrocatalytic activities of Ni-Mo composite electrodes for hydrogen evolution were investigated when the concentration of nano TiO2particles, nano hierarchically porous Ti-SiO2and Al-SiO2particles were4g/L,2g/Land2g/L respectively, the results showed that the electrocatalytic activities of Ni-Mo composite electrodes for hydrogen evolution were better than that of Ni-Mo alloy electrodes, and the electrocatalytic activity of nano hierarchically porous Ti-SiO2/Ni-Mo composite electrode for hydrogen evolution was the best in the three Ni-Mo composite electrodes, that of nano hierarchically porous Al-SiO2/Ni-Mo composite electrode and nano TiO2/Ni-Mo composite electrode were second and third, respectively.3. Ni-Co alloy coatings were prepared by electrodeposition technique in citric acid system. The influence of the main technical parameters on the compositions and the electrocatalytic activities of Ni-Co alloy coatings for hydrogen evolution were investigated, the bright Ni-Co alloy coatings with Co37.75%wt%and Ni62.25wt%were obtained. Nano hierarchically porous hydridosilica particles were prepared by dissolving template. The diameter of nano hierarchically porous hydridosilica hollow microspheres were about70nm, the thickness of hollow microspheres were obout10nm, the specific surface area was896m/g and pore volume was1.30cm/g. Precious metal Pd were successfully load on the nano hierarchically porous hydridosilica hollow microspheres due to the reductibility of silicon hydrogen bonds. The nano hierarchically porous Pd-SiO2particles with hollow structure were analyzed by TEM, the results showed that Pd nanoparticles were distributed in the internal and on the surface of nano hierarchically porous hydridosilica hollow microspheres, the diameter of Pd nanoparticles were about3nm in the internal of nano hierarchically porous hydridosilica hollow microspheres, and the diameter of Pd nanoparticles were from10nm to30nm on the surface of nano hierarchically porous hydridosilica hollow microspheres. Nano hierarchically porous Pd-SiO2/Ni-Co composite electrodes were prepared with nano hierarchically porous Pd-SiO2particles as composite particles. The influence of the concentration of composite particles on the electrocatalytic activities of Pd-SiO2/Ni-Co composite electrodes for hydrogen evolution were investigated by polarization curves, the results showed that the electrocatalytic activities of Pd-SiO2/Ni-Co composite electrodes for hydrogen evolution reached the optimal value when the concentration of nano hierarchically porous Pd-SiO2particles was1.8g/L. The influence of the different components on the electrocatalytic activities of Ni-Co alloy electrodes for hydrogen evolution were investigated, the results showed that the electrocatalytic activities of Ni-Co electrodes for hydrogen evolution were better than that of Ni electrode, and gradually increased with increase in the content of Co in the Ni-Co alloy coatings.4. Ni-Mo-Co alloy coatings were prepared by electrodeposition technique in citric acid system. The influence of the main technical parameters on the compositions and the electrocatalytic activities of Ni-Mo-Co alloy coatings for hydrogen evolution were investigated, the bright Ni-Mo-Co alloy coatings with Ni35.10wt%, Mo50.15wt%, and Co14.75wt%, were obtained. The influence of the different components on the electrocatalytic activities of Ni-Mo-Co alloy electrodes for hydrogen evolution were investigated, the results showed that the electrocatalytic activities of Ni-Mo-Co alloy electrodes for hydrogen evolution were gradually increased with increase in the content of Co and Mo in the Ni-Mo-Co alloy coatings. The electrocatalytic activities of nano hierarchically porous Pd-SiO2/Ni-Co composite electrode, nano hierarchically porous Ti-SiO2/Ni-Co composite electrode and Ni-Mo-Co alloy electrode for hydrogen evolution were investigated, the results showed that the electrocatalytic activity of nano hierarchically porous Pd-SiO2/Ni-Co composite electrode for hydrogen evolution was better than that of Ti-SiO2/Ni-Mo composite electrode, and the electrocatalytic activity of Ni-Mo-Co composite electrodes were better than that of Ni-Mo-Co alloy electrode, the over-potential of hydrogen evolution of nano hierarchically porous Pd-SiO2/Ni-Co and Ti-SiO2/Ni-Co composite electrode decreased80mV and60mV respectively,which were relative to that of Ni-Mo-Co alloy electrode. |
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