Preparation Of Metal Doped Y Zeolite Cathode Material And Electrocatalytic Performance For Hydrogen Evolution In MEC

In recent years,the depletion of fossil energy,the aggravation of environmental pollution and the growing demand for energy all over the world make the search for green energy more urgent.Because of its many advantages,green hydrogen energy has won the attention of many researchers.There are many ways to produce hydrogen,among which microbial electrolysis cell has attracted much attention due to its green and friendly hydrogen production characteristics.Microbial electrolysis cell（MEC）is a potential sustainable new technology developed in recent years.Its principle is to use the metabolic process of microorganisms to decompose a variety of organic compounds and convert them into hydrogen,so as to recover electric energy or hydrogen energy.The selection of cathode catalyst is an important part of MEC system.The ideal cathode catalyst should have the advantages of high catalytic activity and low cost.The results show that the cross-linked network Y zeolite has high specific surface area,short pore and certain cavity structure,which is conducive to the dispersion and effective loading of metal active components,and can improve the local reactant concentration to achieve rapid reaction.In this paper,combined with the advantages of hard and soft template,carbon microspheres as the core,PVP as the adhesive,Nano-Y zeolite as the outer shell were used to prepare Y zeolite（Ya）.The results show that when m（PVP）:m（CSs）=16%,m（CSs@PVP@Y）:V（gel）=1:20,crystallization time is 12 h,the crystallinity of the synthesized cross-linked network Y zeolite is the best,the morphology is spherical structure and highly dispersed,there are cross-linked network cavities inside,and the pore size is mainly distributed in 3.8 nm and 8-10 nm.Cu-Ce-Ya composite was prepared by post impregnation method with Y zeolite as carrier and Cu-Ce bimetallic as active component.A series of electrochemical characterization showed that LSV current response(36.2 A·m^-2)was much higher than that of CP cathode(25.2 A·m^-2)and slightly lower than that of Pt/C cathode(42.7 A·m^-2)when Ce content was 36%（Cu-Ce-Ya-2）,The Tafel slope(46.60 m V·dec^-1)of the Cu-Ce-Ya-2 composite is much smaller than that of the CP cathode,indicating that the the Cu-Ce-Ya-2 composite has a faster charge transfer rate;When the sample was used in MEC,the current density was 16.73 A·m^-2,the proportion of H₂ in the produced gas was 71.05%,and the hydrogen production efficiency was 0.264±0.01 m³·m^-3·d^-1,much higher than that of CP cathode.Although it is slightly inferior to Pt/C cathode in hydrogen production,it shows better catalytic hydrogen evolution performance.In order to simplify the operation steps,improve the work efficiency,reduce the waste of raw materials,and improve the success rate of composite material preparation.Ni-Y zeolite composites and Ce_x-Ni_y-Y zeolite composites were prepared by in-situ synthesis and applied to MEC for hydrogen production.The results show that when the crystallization time is 12 h,the Si/Al ratio is n（Si O₂）:n（Al₂O₃）=16,and the nickel content is n（Si O₂）:n（Ni O）=15,the crystallinity of Ni-Y zeolite is the highest,and the morphology of Ni-Y zeolite is spherical and evenly dispersed;The total specific surface area and pore volume were 467.7 m²·g^-1and 0.255 cm³·g^-1,respectively.The results of electrochemical tests showed that Ni-Y zeolite catalyst showed better hydrogen evolution activity,with Tafel slope of 46.40 m V·dec^-1 and MEC gas production of 23.5±1.12 m L,hydrogen content accounting for 70.72%.Due to the interaction of two metals in bimetallic catalysts,their electronic structure and chemical properties are different from those of single metal catalysts,which will show better performance than single metal catalysts.Therefore,Ce_x-Ni_y-Y zeolite composites were prepared by adding cerium.When n（Ce）:n（Ni）=0.1,the crystallinity of Ce_0.1-Ni-Y zeolite is the highest,and Ni is more dispersed under the action of Ce,and the electrocatalytic activity is the best.Compared with Ni-Y prepared by the same method(maximum current density 35.0 A·m^-2,Tafel slope 44.4 m V·dec^-1 and electrochemical active area 21.8),the electrochemical performance of Ce_0.1-Ni-Y cathode material was significantly improved by adding Ce.The peak current density was 39.8 A·m^-2,Tafel slope was 40.81 m V·dec^-1 and ECSA was51.5 A·m^-2.In order to reveal the effect of Cerium on the activity of hydrogen evolution,the electrochemical characterization and physicochemical properties of the samples were analyzed.The results show that the introduction of cerium makes a strong electronic interaction between nickel and cerium,and increases the number of electrochemical active sites.In addition,the multi-dimensional pore structure of molecular sieves provides great convenience for molecular diffusion,and is also conducive to the overall hydrogen evolution performance of molecular sieves.The results of MEC catalytic hydrogen evolution show that the gas production of Ce_0.1-Ni-Y cathode material is31.2±51 m L,the yield of hydrogen is 0.312±0.013 m³·m^-3·d^-1.The results show that Ce_0.1-Ni-Y has excellent electrocatalytic performance for hydrogen evolution.At the same time,the methane formation rate of Ce_0.1-Ni-Y is slow,and the stable hydrogen yield and purity are maintained in long-term operation.It is expected to provide theoretical and technical support for the further application of hydrogen production from MEC wastewater.