Preparation Of Nickel-based Catalyst And Its Water-decomposition Performance

Today,the global energy structure is transforming to clean and low-carbon,hydrogen energy,as a secondary energy source with wide sources,flexible,efficient,and zero emissions,is a response to energy crisis and environmental pollution,which is an important breakthrough in promoting energy transformation and upgrading.Therefore,the research and development of green and sustainable production of hydrogen energy is particularly important.As for the upstream hydrogen production end,electrolytic water hydrogen production is one of the most effective technology to achieve green hydrogen,and has been used in industrial scale.In this thesis,based on the bottleneck of poor intrinsic activity of nickel-based catalyst,a multi-component composite catalyst was constructed from the structure and component design to improve the activity of hydrogen production from electrolytic water.The specific research content is as follows:（1）The construction of non-noble metal Fe₂O₃@NiO electrode and its application in overall water splitting.In this chapter,a simple and fast microwave deposition method is proposed,and Fe₂O₃@NiO-5composite catalyst is designed and constructed on carbon cloth（CC）.In the hydrogen evolution reaction（HER）,the NiO species in the Fe₂O₃@NiO-x underwent surface reconstruction and evolved into Ni/Ni（OH）₂ with higher activity,which significantly enhanced HER activity.In 1.0 M KOH solution,the required overpotential of the optimized precatalyst Fe₂O₃@NiO-5 was only 295 m V at a current density of10 m A cm^-2.Based on the structural characterization and DFT calculation,it was further found that the reconstructed Ni/Ni（OH）₂ had rapid dissociation ability for H₂O and the optimal adsorption energy for active hydrogen（H*）,which promoted HER kinetics.In the oxygen evolution reaction（OER）,Fe₂O₃@NiO-5 exhibited excellent OER activity due to the effective combination of Fe₂O₃ and NiO layers.The prepared Fe₂O₃@NiO-5 electrode needed an overpotential of 186 m V at 10 m A cm^-2,and exhibited excellent stability for up to 144 hours.The structure characterization of the catalyst showed that Fe₂O₃ and NiO were reconstructed and transformed into Fe OOH and NiOOH with higher activity.In addition,as a bi-functional catalyst,the Fe₂O₃@NiO-5 electrode can provide a current density of 20 m A cm^-2 at a voltage of 1.78 V to drive the water splitting.（2）The preparation of non-precious metal Ni/NiO/CC and the application for overall water splitting.In this chapter,Ni/NiO catalyst was prepared on CC surface by a simple electrodeposition method.The composition of crystalline phase Ni and amorphous phase NiO,the electronic structure of the material surface,the electron transfer rate,and the reaction balance can be regulated systematically and optimized by changing the time and voltage of electrodeposition to promote the water splitting.When the current density is 10 m A cm^-2,the Ni/NiO-2/CC required overpotentials of 74 and 250 m V for HER and OER,respectively,in 1.0 M KOH aqueous solution.At the same time,as a bifunctional catalyst,the Ni/NiO-2/CC||Ni/NiO-2/CC electrode required only 1.57 and 1.88 V to drive 10 m A cm^-2 and 100 m A cm^-2towards the water splitting.（3）The preparation of multi-component Ni-NiO/Fe（OH）₃/CC composite catalyst and the application for overall water splitting.In order to further improve the catalytic activity of Ni-NiO electrode,in this chapter,Fe（OH）₃/CC composite catalyst with double heterostructure（Ni-NiO,NiO-Fe（OH）₃）was constructed by introducing Fe（OH）₃ into Ni/NiO system via the electrodeposition and chemical precipitation.The Ni-NiO/Fe（OH）₃-3/CC exhibited excellent OER and HER activities due to its unique structure and multi-component advantages.At the current density of 10 m A cm^-2,the Ni-NiO/Fe（OH）₃-3/CC required overpotentials of 220 and 66 m V for OER and HER,respectively.In addition,as a bi-functional catalyst,the Ni-NiO/Fe（OH）₃-3/CC composite can drive 10 m A cm^-2 and 100m A cm^-2 to produce hydrogen at low voltages of 1.52 V and 1.72 V towards the water splitting,while running stably for more than 40 hours.