Preparation Of Nickel Base-like Layered Double Hydroxides Electrode And Its Application In Seawater Electrolysis

To alleviate the increasingly severe global energy and environmental crisis and achieve sustainable development goals of"carbon peak"and"carbon neutrality,"it is imperative to adjust the energy structure.This involves gradually substituting the currently dominant fossil fuels with clean,renewable green energy sources.Hydrogen energy,as an environmentally friendly new energy source,stands out due to its high calorific value,making it an ideal alternative to fossil fuels.Electrolysis of water for hydrogen production is the most extensively researched method.However,the slow kinetics of the Oxygen Evolution Reaction(OER)in this process,limited by the anodic catalytic activity and stability,poses significant challenges for its large-scale industrial application.In contrast to electrolyzing freshwater,which consumes scarce freshwater resources,direct electrolysis of seawater presents a more viable hydrogen production method.Nevertheless,the abundant chloride ions(Cl~-)in seawater inevitably corrode equipment and produce toxic substances during production,necessitating the development of an anodic OER catalyst with high catalytic activity and selectivity.This study focuses on nickel-based layered double hydroxides,using foam nickel as a substrate to develop various self-supporting electrodes for seawater electrolysis.The main contents and results of this study are as follows:(1)A sulfur-doped nickel-chromium layered double hydroxide self-supporting electrode(S-doped NiCr-LDH/NF)was synthesized using a one-step method with trichloride chromium and sodium thiosulfate as raw materials.The material was characterized using X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and X-ray photoelectron spectroscopy(XPS).Electrochemical methods such as cyclic voltammetry,linear sweep voltammetry,and electrochemical impedance spectroscopy were employed to study the catalyst’s OER performance.The reaction time,solution concentration,and the amount of sodium thiosulfate added significantly influenced the sample’s catalytic performance.The results showed that the S-doped NiCr-LDH/NF self-supporting electrode,prepared under conditions of 2 hours reaction time,1 mol/L solution concentration,and 0.03 g sodium thiosulfate,exhibited an overpotential of 270 mV at 100 mA/cm~2current density in alkaline freshwater(1 M KOH),295 mV in simulated alkaline seawater(1M KOH+0.5 M Na Cl),and 332 mV in real alkaline seawater(1 M KOH+seawater).(2)A sulfur-doped nickel-iron layered double hydroxide self-supporting electrode(S-doped NiFe-LDH/NF)was synthesized using a one-step method with ferric chloride and sodium thiosulfate as raw materials.The material was characterized using techniques such as XRD,SEM,TEM,and XPS,followed by a series of electrochemical tests.The reaction time,solution concentration,and the amount of sodium thiosulfate added were crucial for the sample’s catalytic performance.The results indicated that the S-doped NiFe-LDH/NF self-supporting electrode,prepared under conditions of 5minutes reaction time,0.5 mol/L solution concentration,and 0.05 g sodium thiosulfate,demonstrated excellent OER catalytic performance in all three electrolytes and maintained good stability for over 130 hours in real alkaline seawater(1 M KOH+seawater).(3)The sulfur-doped nickel-iron layered double hydroxide self-supporting electrode was used as the anode,with foam nickel as the cathode,for direct electrolysis of seawater to produce hydrogen.The results showed that at current densities ranging from1000-6000 A/m~2,the voltage significantly decreased and stability improved when the anode was switched to the prepared self-supporting electrode,compared to using foam nickel for both anode and cathode.