Enhanced Water Electrolysis Performance Of Metal Phosphide Based On Interface Engineering Regulation

As human industrialization continues to advance,the form of energy demand and supply is becoming more and more severe,and the pollution problems brought by rapid industrialization to water bodies in the environment are becoming more and more serious.Therefore,focusing on new sources of sustainable energy and treating wastewater in the environment has become an urgent problem to be solved.Hydrogen energy has the advantages of no pollution and high calorific value,and is considered one of the most promising alternatives to replace fossil fuels such as oil.Hydrogen production by electrolysis of water is currently the most important method to produce green hydrogen.However,there are some problems in the cost of hydrogen production by electrolysis:among them,the high overpotential of hydrogen evolution reaction（HER）at the cathode and oxygen evolution reaction（OER）at the anode increases the overall energy consumption of electrolytic water;in addition,the oxygen production reaction at the anode with high potential in electrolytic water is the rate-limiting step of water decomposition,and the low value-added oxygen produced is not easy to be utilized.To address these problems,on the one hand,a high catalytic activity electrocatalyst was designed to reduce the overpotential of the reaction,and on the other hand,replacing the kinetically slow OER with anode contaminant degradation to reduce the voltage required for driving.Therefore,this work focuses on the problem of high energy consumption in the electrolysis of water,and the study of catalytic activity of electrode hydrogen precipitation and anodic oxidation for degradation of urea wastewater was carried out from the two aspects mentioned above.On the one hand,the heterogeneous structure of Ru-Ru₂P electrocatalyst was prepared by interfacial engineering modulation,and the high catalytic activity of hydrogen precipitation catalyst achieved efficient hydrogen production by hydrolysis under alkaline conditions.On the other hand,Cl·mediated anodic oxidation reaction was used to replace OER for effective degradation of urea wastewater.The main research works are as follows:1.To address the problem of low activity and unstable performance of cathodic hydrogen precipitation electrocatalysts at high current densities,we have successfully prepared efficient Ru-Ru₂P heterogeneous nanoparticle hydrogen precipitation electrocatalysts by using the strong ion replacement ability of Ca²⁺in hydroxyapatite（HAP）and in situ green phosphorylation with its own inorganic phosphorus source as the green phosphorus source in a two-step strategy.Theoretical calculations showed that electron redistribution occurred at the heterogeneous interface of Ru-Ru₂P,thus modulating the electronic structure of Ru-Ru₂P to achieve the optimal hydrogen adsorption strength.The HER overpotential(η₁₀)of Ru-Ru₂P under alkaline electrolyte is only 24 mV,and it can operate stably at high current density(>1000 mA cm^-2)for120 h.Meanwhile,based on the three-dimensional network structure of HAP nanowires,HAP membrane with high flexibility were prepared,and Ru-Ru₂P as the cathode catalyst and Ni Fe-LDH/CNTs as the Anode catalysts were assembled into membrane electrodes with sandwich structure and zero gap,respectively.The constructed home-made（-）Ru-Ru₂P||Ni Fe-LDH/CNTs（+）membrane electrode electrolyzer has excellent total water dissolution performance and requires only 1.53 V to drive a current density of 10 mA cm^-2.2.To address the problems of slow kinetics of anodic oxygen evolution reaction and low economic value of the product oxygen,we designed anodic degradation of urea wastewater instead of OER.Specifically,well-aligned Co-MOF（ZIF-L-Co）nanosheets were grown on conductive 3D substrate carbon cloth,then in situ etched in ethanol solution containing Co²⁺to obtain defect-rich ultrathin Co（OH）₂ nanosheets,and finally they were further calcined in air to obtain oxygen-rich vacancy-deficient D-Co₃O₄.It was found that the calcination temperature had an important effect on the catalytic performance of the D-Co₃O₄ series catalysts had an important influence on the catalytic performance,and the best anodic degradation performance of D-Co₃O₄ was obtained at a calcination temperature of 350℃.The effect of oxygen vacancies on urea degradation was also investigated.The Co²⁺/Co³⁺cycle in D-Co₃O₄ activates the Cl^-in urea to Cl·thus completing urea degradation rapidly.Oxygen vacancies generate positive charge in the Co center and the introduction of oxygen vacancies leads to faster Cl·yield.By investigating the working voltage,pH and NaCl concentration,it was shown that 97.14%removal of urea from simulated wastewater could be achieved within 45 min at an operating voltage of 2 V,pH=7 and 50 mM NaCl.