Preparation Of Nano-RuO2 Catalyst And Its Application In Green Electrosynthesis Of Hypophosphorous Acid

Hypophosphorous acid is an important chemical raw material,and have a wide range of applications in the fields of electroless plating,machinery,aerospace,organic synthesis and medicine,etc.The mainly preparation methods of hypophosphorous acid is as follows:reaction of yellow phosphorus with alkali metal or alkaline earth metal hydroxide,ion exchange method and electrolysis.When used the above methods to prepare hypophosphorous acid,that obtained concentration of hypophosphorous acid is low,cumbersome process,and the subsequent separation and enrichment process is complex.Its production has resulted in a large number of three wastes,resulting in environmental pollution,so it is difficult for large-scale production and application.The electrochemical method solves the shortcoming of the above methods.Due to the electrolysis can reduce energy consumption,it is low preparation cost and environmentally friendly.Therefore,electrolysis has attracted more and more attention and favor.We inspired by fuel cells and metal air batteries,the gas diffusion electrode was applied to prepare hypophosphorous acid by electrolysis.The gas diffusion electrode oxidizes hydrogen at the anode compared with the traditional electrolyzed water,which reduces the electrode potential and saves energy and reduces consumption.At the same time,the mainly contents and results are as follows:?1?Nano-RuO₂ electrocatalysts were prepared by solvothermal preparation of different solvents?ethanol,propanol,isopropanol and n-butanol?.The nano-sized catalyst was characterized by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,transmission electron microscopy?TEM?,and X-ray photoelectron spectroscopy?XPS?.At the same time,the electrochemical performance of the catalyst was investigated by cyclic voltammetry?CV?.The results showed that the catalyst prepared by different solvents exhibits irregular morphology.Among all of four catalysts,the catalyst prepared in ethanol,n-propanol and isopropanol has higher dispersibility,while n-butanol has poor dispersibility.XRD analysis showed that the catalyst prepared by ethanol,propanol and n-butanol was a mixture of Ru and RuO₂,and in different solvent the order of Ru element content was:n-butanol>ethanol>propanol.The catalyst prepared by isopropanol was pure RuO₂.From the TEM image we can conclude that the catalyst prepared by the four solvent exist the agglomeration phenomenon.Electrochemical test studies showed that the oxidation performance of hydrogen decreases with the increase of Ru elemental content.In different solvent the catalytic activity of the catalyst for hydrogen oxidation is isopropanol>propanol>ethanol>n-butanol.The use of isopropanol as a solvent had the best performance for hydrogen oxidation when the concentration RuCl₃ was 0.15 M and the hydrothermal temperature was 160°C?2?The effect of solvothermal temperature,RuCl₃ concentration and solvothermal time on the performance of the catalyst were investigated by orthogonal experiments.The solvothermal reaction conditions with the concentration RuCl₃ was0.15 M,the solvothermal reaction temperature was 170°C and the reaction time was3 h that had the best performance.The catalyst was characterized by SEM and XRD.The catalyst prepared under optimal conditions have good crystallinity and its amorphous morphology is very well.The catalyst had the best catalytic activity.?3?We prepared of hydrogen oxidizing gas diffusion electrode.The performance of the gas diffusion electrode was controlled by the different types of carbon black?VX-72R,acetylene black,activated carbon?,pore former?NaCl,Na₂SO₄,activated carbon?and the ratio of polytetrafluoroethylene?PTFE?emulsion.The gas diffusion layer was optimized from two aspects:hydrophobicity and permeability.The performance of the catalyst layer was controlled by the different types of carbon black?VX-72R,acetylene black,activated carbon?,the loading of the catalyst,and the proportion of the PTFE emulsion.It was found that the gas diffusion layer adopts4:3:3 VX-72R carbon black:NaCl:PTFE emulsion and the catalyst loading in the catalytic layer is 6 mg·cm^-2 has the best performance.?4?Nano-RuO₂ gas diffusion electrode is applied in green electrosynthesis hypophosphorous acid.Compared with titanium-based coating electrode?DSA?that the gas diffusion electrode can reduce voltage and effectively save energy.As the temperature of the solution increases,the current efficiency and the conversion rate of sodium hypophosphite gradually increase.When the temperature of the solution research 50°C,the current efficiency and the conversion rate of sodium hypophosphite decline.The optimal preparation conditions are:current density 30mA·cm^-2,temperature 45°C,and initial concentration of sodium hypophosphite 300g·L^-1,current efficiency can reach 82.2%.The conversion rate of sodium hypophosphite can reach 28.7%.