Electrochemical Water Splitting To Produce Hydrogen And Hydrogen Peroxide And Its Degradation Of Organic Pollutants

Electrochemical water splitting for hydrogen production can convert electrical energy into hydrogen energy and is an effective method for producing green hydrogen.In the traditional electrochemical water splitting reaction,hydrogen is precipitated at the cathode,and the anode product is oxygen.Compared with hydrogen,the oxygen produced by the water electrolysis anode has lower application value;the simultaneous production of oxygen and hydrogen in electrolytic cell will also lead to subsequent gas separation problems.Water can be converted to H₂O₂ through a 2-electron oxidation reaction,but this reaction is thermodynamically more difficult to occur than the 4-electron oxygen evolution reaction.In recent years,it has been reported in the literature that the 2-electron oxidation of water can be indirectly obtained in the electrolyte containing bicarbonate to obtain H₂O₂.On the whole,domestic and foreign scholars have focused on the research on hydrogen production from water electrolysis and H₂O₂ production from water electrolysis in a relatively isolated manner,and have not been able to effectively combine the two studies.In view of this background,this thesis proposes a reaction system for the simultaneous production of hydrogen and H₂O₂ by electrochemical water splitting according to the reaction principles of electrolysis of water to hydrogen and H₂O₂ from water.The effect and related laws of the substance.The main research contents and conclusions of the paper are as follows:（1）The effect and related laws of WO₃ and graphite as anode materials for electrochemical water splitting to simultaneously produce hydrogen and H₂O₂ were comparatively studied.In contrast,due to the electrolytic corrosion of WO₃,graphite was more suitable for long-term electrolytic H₂O₂ reaction in HCO₃^-containing electrolyte.The electrolytic cell constructed with graphite sheet as cathode and anode can produce high-purity H₂ on the graphite cathode,and the reaction Faradaic efficiency was about 99%.At the same time,H₂O₂ can be obtained indirectly on the graphite anode:after 60 minutes of continuous reaction,about 950 ppm of H₂O₂ can be obtained in 1.0 M K₂CO₃ electrolyte;325 ppm of H₂O₂ can also be obtained in 1.0 M KHCO₃ electrolyte H₂O₂.The ¹³C nuclear magnetic resonance detection of the electrolyte found that the HCO₄^-（δ=158.5）¹³C NMR signal appeared after the constant pressure electrolysis reaction of the electrolyte containing HCO₃^-and CO₃^2-,which proved that the electrochemical oxidation of HCO₃^-to HCO₄^-is mediated by water.The main route of 2-electron oxidation to produce H₂O₂.Further electrochemical strips showed that H₂O₂ is not stable in HCO₃^-or CO₃^2-containing electrolytes,and there is a simultaneous electro-oxidative decomposition process（2 H₂O₂→2 H₂O+O₂,E^Θ=0.695 V vs.RHE）during the generation process,thus leading to electrolysis the concentration of H₂O₂produced does not increase continuously with the reaction time.（2）Based on the reaction characteristics of graphite-based electrolytic cells to prepare H₂O₂ in HCO₃^-or HCO₃^2-containing electrolytes,an electro-Fenton reaction system was constructed to degrade organic pollutants in water.The comparative study found that 50 ppm methylene blue and 20 ppm phenol can be rapidly degraded in KHCO₃ and K₂CO₃electrolytes,while their degradation rates are low in Na₂HPO₄,Na H₂PO₄ and Na₂SO₄ electrolytes.Electron spin resonance detection shows that there are high-intensity·OH signals in K₂CO₃/H₂O₂ and KHCO₃/H₂O₂ solutions,indicating that·OH is the main active species during the degradation of organic matter in water in HCO₃^-or HCO₃^2-electrolytes.Further comparison found that HCO₃^-has an important activation effect on the electrochemically generated H₂O₂,which can promote its conversion to·OH.According to the characteristics of HCO₃^-activated H₂O₂ as·OH process,an intermittent pulsed electro-Fenton reaction pathway is innovatively proposed.The intermittent pulse is used to promote H₂O₂ to be fully activated and converted to·OH,so as to achieve high-efficiency and energy-saving degradation of organic matter in water.The electrochemical water splitting reaction system proposed in this paper to simultaneously produce hydrogen and H₂O₂,as well as the in-situ electrochemical production of H₂O₂ for the degradation of organic pollutants in water.Useful method and theoretical reference.