Preparation Of Carbon Coupled Nickel-iron Based Electrodes And Performance For Seawater Electrolysis

Electrocatalytic seawater splitting to hydrogen production technology is of great significance for clean energy storage and protection of fresh water resources.However,at a high potential,chlorine evolution is easily to compete with oxygen evolution reaction at the anode of seawater electrolysis,which not only reduces the electrolysis efficiency but also brings the hidden danger of production safety.Besides,Ca²⁺,Mg²⁺and microbials can easily reduce the reactivity and the service life of the catalysts,which limits the application and development of seawater electrolysis.It is of great significance to develop stable anode catalysts with high oxygen evolution selectivity to promote the development of hydrogen production by seawater electrolysis.Nickel-Iron based materials have great potential as anodic electrocatalysts for seawater electrolysis due to their excellent OER reactivity.However,poor electrical conductivity,insufficient exposure of active sites and poor mass transfer ability severely limit the development of nickel-iron based materials.Herein,we adopted the strategies of regulating the morphology structure,increasing exposure of active sites and improving the mass transfer to develop two kinds of carbon coupled nickel-iron based electrocatalysts,which can effectively inhibit the chlorine evolution reaction during the seawater electrolysis.The main research contents and results are as follows:Using strong hydrolysis capacity of Fe³⁺,a Fe OOH-modified NiFeLDH precursor(Ni_0.82Fe_0.18)was grown on the carbon fiber substrate by hydrothermal method,Ni_0.82Fe_0.18-EA was obtained by further electrochemically activated.The effects of Fe³⁺and electrochemical activation process on microstructure,composition and electrochemical performance were well investigated.The results showed that appropriate introduction of Fe³⁺is beneficial for enhancing the electrochemical activity.Fluoride ion would leach and induced surface reconstruction of the nanosheet during the electrochemical activation process,exposure of more edge sites and pore structure.The electrochemical activity of Ni_0.82Fe_0.18-EA electrode is greatly enhanced by the addition of active sites and the diffusion ability of electrolyte.The Ni_0.82Fe_0.18-EA can continuously deliver large current density of 600 m A·cm^-2 more than 50 h in alkaline simulated seawater and 100 m A·cm^-2 for 48 h in alkaline seawater,showing excellent selectivity of oxygen evolution and operational stability in seawater electrolysis.NiFeMo nanosheets were grown vertically and orderly on surface of carbon fiber by hydrothermal method.Then,amorphous NiFeMoP electrode was obtained by further phosphated.The effects of molybdenum species and phosphating temperature on the crystal structure,morphology and electrochemical performance were investigated.The results shows that molybdenum species induces Ni²⁺and Fe³⁺to form amorphous structure,which is conducive to the full exposure of active sites.Appropriate introduction of molybdenum species can improve reactive activity.The introduction of PO₄^3-can not only optimize the charge distribution of the material,but also resist the diffusion of chloride ions to the electrode surface,thus improving the oxygen evolution selectivity.In alkaline simulated seawater electrolyte,the NiFeMoP electrode can deliver current density of 100 m A·cm^-2 at overpotential of 268 m V for more than 72 h.When NiFeMoP electrode is used for overall seawater splitting,the electrochemical activity is far better than that of Ru O₂ and Pt/C combination as well as shows excellent operation stability.In addition,different substrates supported amorphous nickel-iron molybdenum phosphide electrodes all show excellent performance in alkaline simulated seawater electrolysis,which indicates that the synthesis method has a certain universality...