The Preparation Of Ni And Co Nanomaterials And The Study Of Their Catalytic Behavior For The Electrooxidation Of H₂O₂ And NaBH₄

Fuel cell is a kind of energy conversion device which directly converts the chemical energy in fuel and oxidant to electric energy.It has attracted wide attention due to the characteristics of cleanliness and high efficiency.As two new environment-friendly fuels,H₂O₂ and NaBH₄have the advantages of high safety and easier to store and transport compared with traditional H₂ fuel.As one of the core components of fuel cells,electrode materials play a decisive role for the performance of fuel cells.Nowadays,the electrode materials employing noble metals as catalysts exhibit superior electrochemical activity.However,the commercial application is severely restricted because of its limited reserves and high cost.In order to overcome this problem,it is urgent to prepare non-noble metal electrode materials with high catalytic activity for fuel cells.Based on this,transition metal Ni and Co catalysts were prepared by different methods to catalyze the electrooxidation of H₂O₂ and NaBH₄.The details are as follows:Ni-SiO₂/CP electrode was prepared by electrodepositing Ni-SiO₂ composites on carbon paper?CP?substrates,and then partial SiO₂ was removed by dealloying to make Ni-SiO₂/CP?AD?electrode with three-dimensional?3D?porous structure to catalyze the electrooxidation of H₂O₂.The prepared Ni-SiO₂/CP?AD?electrode has high specific surface area and good gas-liquid mass transfer characteristic.The electrochemical performance of Ni-SiO₂/CP?AD?and Ni/CP electrodes were tested,and the results show that Ni-SiO₂/CP?AD?electrodes have better catalytic performance.In addition,the effects of deposition potential,deposition time and composition of deposition solution on the catalytic performance of Ni-SiO₂/CP?AD?electrodes were investigated,which provide a certain guiding sense for the preparation of Ni-SiO₂/CP?AD?electrodes with high catalytic activity.The Co-P alloy was successfully deposited on the copper foam?CF?substrate by electrodeposition and used to catalyze NaBH₄ electrooxidation.During the electrodeposition process,H₂ bubbles released from the cathode were used as dynamic templates to make the prepared Co-P/CF electrodes own 3D porous structure.Scanning electron microscopy?SEM?characterization showed that there were more nanoclusters on the surface of Co-P/CF electrode than that of Co/CF electrode,indicating that the introduction of P element created more Co catalytic active sites on the surface of the electrode,which provided a guarantee for Co-P/CF electrode with the high NaBH₄ catalytic activity.Cyclic voltammetry?CV?tests were performed for the prepared Co-P/CF and Co/CF electrodes at room temperature,and the current density of the Co-P/CF electrode was 2.73 times that of the Co/CF electrode.In this paper,the effects of different preparation conditions?deposition potential,deposition time and composition of deposition solution?on the catalytic performance of electrodes were also investigated.The Co nanoparticle particles with uniform particle size distribution were prepared by Impinging Stream Rotating Packed Bed?IS-RPB?a new type of high gravity new reactor developed by our laboratory.The Co catalyst was loaded onto the nickel foam?NF?substrate by the method of"soaking-drying-pressing",and the Co/NF?IS-RPB?electrode with high catalytic activity towards NaBH₄ electrooxidation was successfully prepared.The particle sizes of Co nanoparticles prepared by IS-RPB reactor and traditional stirred reactor?TSR?under normal gravity were characterized by nanometer particle size analyzer.The results showed that the particle size of Co nanoparticles prepared by IS-RPB reactor was small and uniform,which provided a guarantee for the high specific surface area of Co/NF?IS-RPB?electrode.Besides,Co/NF?TSR?electrodes were fabricated by using Co nanoparticles prepared by TSR reactor.The electrochemical measurements of Co/NF?IS-RPB?electrode and Co/NF?TSR?electrode were carried out and the results show that the current density of Co/NF?IS-RPB?electrode is530 mA·cm^-2,which is 1.93 times of that of Co/NF?TSR?electrode.It is noteworthy that Co nano-powder particles were prepared by IS-RPB reactor in this experiment.The process is simple,the nano-powder particles are prepared with small and uniform size,and can realize continuous production,which has great industrial application prospects.