Preparation Of Cobalt-based Nanocatalysts And Their Applications Of Oxygen Evolution Reaction

Electrochemical water splitting is a sustainable hydrogen energy conversion,storage,and transportation technology.Among them,the oxygen evolution reaction(OER)plays a key role in electrocatalysis.In the process,researchers have been working to develop low-cost,earth-rich,efficient and stable OER electrocatalysts.In this thesis,the electrocatalytic oxygen evolution reaction is used as the guide,and through the preparation of cobalt-based nano-interface composites,the synthesis of an electrocatalyst with high catalytic activity and stability is achieved.Furthermore,the combination of experiments and theoretical calculations is used to study the structure-activity relationship of materials and the basic mechanism of OER.The discussion provided will help to explore and develop better electrocatalysts,provide valuable directions and promising approaches in the field of energy conversion,and promote the development of electrocatalytic water splitting systems.The main contents are as follows:(1)In this chapter,a uniform array of Co nanowire precursors was prepared on a carbon cloth(CC)by a chemical bath deposition method.According to the Kirkendall effect,a hollow Co₉S₈ nanotube was obtained by anion exchange using a hydrothermal reaction.Grow in situ on CC to avoid the blocking of active sites caused by the use of binders.After structural characterization and electrochemical testing,it was found that the highly conductive Co₉S₈ nano-hollow tube structure provides rich catalytic active sites and accelerates the catalysis.The ion diffusion rate and electron transmission rate during the process have improved the electrocatalytic OER performance of the Co₉S₈ electrode,with an overpotential of 312 m V at 10 m A cm^-2 and a Tafel slope of 127 m V dec^-1,and within20 h There is almost no degradation in performance,and it has good long-term stability.(2)Based on(1),this chapter uses a simple electrodeposition method to uniformly load a layer of nickel-iron layered hydroxide(NiFe-LDH)onto Co₉S₈ nanotubes to achieve efficient OER performance.The obtained electrode material is composed of a three-layer structure:a carbon cloth(CC)as a substrate at the bottom,a Co₉S₈ nanotube arranged vertically as an intermediate layer,and NiFe-LDH as an outermost layer.Through morphological control and surface loading,on the one hand,an interfacial interaction occurs between the highly conductive Co₉S₈ and NiFe-LDH,which promotes charge transfer and improves the conductivity of NiFe-LDH,thereby improving the OER catalytic performance of the overall electrode material;Co₉S₈ nano-tubes increase the specific surface area of the substrate,which results in more NiFe-LDH loadings,more catalytically active sites,and accelerated OER catalytic processes.Therefore,the interface material shows significant OER catalytic activity under the synergistic effect of Co₉S₈ and NiFe-LDH,and has a low overpotential of 219 m V and a small Tafel of 55 m V dec^-1 at a current density of 10 m A cm^-2.Slope.The method for preparing nanotubes and surface deposition can be extended to other metal material systems,and has been widely used in the fields of fuel cells.(3)Considering that the electronic interaction at the interface is a good strategy to improve the electrocatalytic performance of OER,we consider the use of organic molecular adsorption for further optimization and modification of interface materials.In this chapter,the interface material between nickel hydroxide and cerium dioxide(EG-Ni(OH)₂@Ce O₂)was optimized by adsorption of ethylene glycol.The structural characterization and theoretical calculations confirmed that the nickel-cerium interface induced by ethylene glycol was stronger.Electron interactions have generated a large number of Ni^(3-?)+active sites,reduced the energy reaction barrier,and increased the OER reaction kinetics rate in the catalytic system.Electrochemical tests show that EG-Ni(OH)₂@Ce O₂ has excellent OER performance,showing low overpotential(335 m V)and small Tafel slope(67.4 m V dec^-1)at50 m A cm^-2,at 10 It also maintains stability up to 60 h at 20 and 30 m A cm^-2.This study demonstrates the importance of metal material interface engineering based on organic solvent adsorption to improve the electrocatalytic OER process.