| Due to the advantages of clean,pollution-free and renewable,hydrogen energy is widely welcomed in society with severe environmental pollution.Sodium borohydride is an excellent hydrogen storage material,and it is also the first choice of hydrogen source for fuel cells,but its widespread use is limited due to high production costs.The electrochemical method is used to convert sodium metaborate to sodium borohydride,and the recycling of boron resources has become the focus of research.Due to the repulsive effect of the cathode on BO2-,the focus of the conversion of sodium metaborate to sodium borohydride is to select the appropriate power supply mode and the electrode with high catalytic activity as the cathode material.In this paper,Ce-Ni-B rare earth alloy electrode and Tb-Ni-B rare earth alloy electrode with corrosion resistance and catalytic activity were prepared.The effect of the addition of rare earth on the surface morphology,composition and corrosion resistance of the electrode was studied.Ce-Ni-B rare earth alloy electrode and Tb-Ni-B rare earth alloy electrode were used as cathode materials for electrolytic sodium metaborate.Study on the electrocatalytic reduction behavior of sodium metaborate under different conditions.The main research contents are as follows:1.Electroless nickel-plated rare earth alloy electrode.Through orthogonal experiments and existing literature formulas,the optimal plating solution formula for electroless Ni-B alloy plating was determined to be 10g/L of dimethylaminoborane,1g/L of sodium hydroxide,and 10g/L of anhydrous nickel chloride,Malic acid 1.5g/L,citric acid 1.5g/L,and oxalic acid 1.5g/L.Ce-Ni-B and Tb-Ni-B rare earth alloy electrodes were prepared by adding different contents of Ce?NO3?3 and Tb?NO3?3 to the optimal plating solution of Ni-B alloy.The experimental results show that with the addition of 3g/L of rare earth nitrate,the surface of the rare earth alloy electrode is flat and dense,and the surface morphology is the best.The addition of Ce3+and Tb3+changed the surface composition of Ni-B alloy coatings.The corrosion resistance of Ce-Ni-B and Tb-Ni-B rare earth alloy electrodes in sodium hydroxide solution was studied by electrochemical method and full immersion corrosion experiment.The results show that Ce-Ni-B and Tb-Ni-B rare earth alloy electrodes have the best corrosion resistance after adding 3g/L of rare earth nitrate.2.A qualitative analysis of sodium borohydride was performed on the Au electrode by cyclic voltammetry,and a clear and stable BH4-characteristic oxidation peak was found at-0.52V.An Au electrode peak current method was established to determine the concentration of trace sodium borohydride in the electrolyte.When the concentration range of sodium borohydride detected was 1×10-4 mol/L9×10-4 mol/L,the linear regression equation of sodium borohydride concentration and peak current value of sodium borohydride was obtained as y=0.03505x+9.5×10-8.3.The linear scanning voltammetry and cyclic voltammetry were used to study the electrochemical behavior of sodium metaborate.The results showed that BO2-did not directly participate in the cathodic reduction process.The electrochemical reduction process of BO2-is most likely an indirect reduction mechanism.4.Using Ce-Ni-B rare earth alloy electrode as the working electrode,the electrocatalytic reduction of sodium metaborate was studied by adjusting a series of process conditions such as power supply mode,forward pulse voltage,and reverse pulse voltage.The optimal electrolysis conditions for sodium metaborate are obtained:Power supply mode selection pulse electrolysis,the cathode chamber is a mixed solution with a concentration of 0.5mol/LNaBO2+1mol/LNaOH,the anode chamber is a 1mol/L NaOH solution,and the forward pulse voltage-1.5V,forward pulse time is3s,reverse pulse voltage is 0.5V,reverse pulse time is 2s,electrolysis time is 4h,the maximum concentration of sodium borohydride in the electrolyte is 3.97×10-4 mol/L,current sensitivity is 1mA.Additive thiourea has no effect on electrolysis.5.Tb-Ni-B rare earth alloy electrode was used as the working electrode.The effects of pulse current frequency,electrolysis time and additives on the electrocatalytic reduction of sodium metaborate were studied.The results show that when T1=3s,T2=2s and the electrolysis time is 4 hours,the maximum concentration of sodium borohydride electrolyzed is 5.1×10-4mol/L.The electrocatalytic activity of Tb-Ni-B rare earth alloy electrode is better than that of Ce-Ni-B rare earth alloy electrode under the same electrolytic conditions.When thiourea was added to the electrolyte,the concentration of sodium borohydride electrolyzed was 7.4×10-4mol/L,and the electrolysis efficiency was significantly improved. |
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