Study On The Synthesis And Electrocatalytic Oxygen Exolution Performance Of Nickel-Based Nanocomposites

With the rapid development of the global economy,the demand for energy is also increasing.As a traditional energy source,fossil fuels are deficient in reserves,harmful to the environment,and produce a large amount of greenhouse gases.Therefore,finding new energy sources that can replace it has become the key to solving energy problems.Due to the inherent safety,environmental superiority,and abundant resources,hydrogen energy stands out among various energy technologies and is considered to be a promising alternative to traditional fossil fuels in the future because of its clean,pollution-free and high energy density.As an important method of hydrogen production,water splitting is simple,economical,and environmentally friendly,and other hydrogen production methods often rely on fossil fuels,so the production of hydrogen from water splitting is the most promising way to produce hydrogen energy.The desire to develop a sustainable hydrogen economy has inspired scientists in the field of materials and energy to study on the electrocatalytic water decomposition to provide stable and renewable hydrogen energy.Since electrocatalytic reactions play a central role in energy preparation,conversion and storage,the preparation and performance of electrocatalytically nanomaterials have become an important research area.Currently,catalysts for water electrolysis have been extensively studied to provide pure hydrogen by improving energy conversion efficiency.The oxygen evolution reaction(OER)is a slow four-electron transfer process that requires a high energy barrier to break O-H bond,therefore,the electrocatalyst for oxygen evolution reaction has important application value in the development and utilization of renewable energy.Currently,most OER catalysts are based on precious metal oxides such as iridium oxide(IrO2)and ruthenium oxide(RuO2).Due to the scarcity and expensiveness of precious metal materials,there is an urgent need to replace them with more cost-effective materials such as transition metal compounds.In this paper,the following two catalyst materials were synthesized and their oxygen evolution properties were studied.(1)The nickel-based metal oxide composite electrocatalysts with unique interface and electronic structure are designed for electrocatalytic oxygen evolution reaction.By optimizing the metal oxide through the lithium-induced conversion reaction,metal/metal oxide composites with rich interfaces and excellent conductivity were prepared,which increased the catalytic active sites and accelerated the mass transfer during the electrocatalytic reaction.In this experiment,the OER performance of the composite catalysts including NiCo/NiCo2O4,NiMn/NiMn2O4 and CoMn/CoMn2O4 have been significantly improved.This work also uses in-situ Raman spectroscopy to explore the catalytic mechanism of the catalysts,revealing the active center of the catalyst during the oxygen evolution process and the synergy between the metal and the metal oxide.(2)The phosphorous-doped nickel sulfide(Ni3S2@Ni5P4)composite material was synthesized by a simple hydrothermal method and used as catalyst for the oxygen evolution reaction in alkaline electrolyte.The synthesized Ni3S2@Ni5P4 composite catalyst showed excellent OER activity with an overpotential of 399 mV at a current density of 50 mA cm-2.In alkaline media,the slope of Tafel is 82 mV dec-1,and the catalytic stability exceeds more than 15 hours.In addition,Ni3S2@Ni5P4 showed better catalytic performance than primary nickel sulfide and nickel phosphide series catalysts.This is mainly due to the synergistic effect of Ni3S2 and Ni5P4 in the composite structure to accelerate electron conduction and enrich active sites.