花生壳基多孔碳负载Pd-Co催化剂应用于碱性介质中电氧化甲醇.pdf

第39卷第10期2023年10月Vol.39 No.1020202032无机化学学报CHINESE JOURNAL OF INORGANIC CHEMISTRY收稿日期：20221215。收修改稿日期：20230825。广州市基础与应用基础项目(No.202102020424)、大学生创新创业训练计划项目(No.S202214278030)、广东省科技创新战略专项资金(“攀登计划”项目，No.pdjh2022b0385)、广东省普通高校重点科研项目(No.2021KCXTD086)和广东省普通高校特色创新项目(No.2022KTSCX090)资助。通信联系人。Email：花生壳基多孔碳负载PdCo催化剂应用于碱性介质中电氧化甲醇霍朝晖,1,2韦雪蓉1黄勇1陈泽宇1陈伟冰1张绮彤1张刚3温耿龙1石俊杰1(1广东第二师范学院化学与材料科学学院，广州510303)(2广东高校先进材料与节能减排工程技术开发中心，广州510303)(3深圳方润环境科技有限公司，深圳518107)摘要：以花生壳为原料，经KOH活化制备花生壳基多孔碳(HC)。氮气吸附-脱附研究表明，所获得的多孔碳的总表面积高达1 645 m2g-1。采用浸渍还原法制备了以HC为载体的PdCo/HC催化剂。X射线衍射(XRD)和X射线光电子能谱(XPS)分析表明，催化剂中的Co主要以Co和CoO的形式存在，Co进入Pd的晶格并形成PdCo合金。PdCo/HC0.5700的透射电子显微镜(TEM)结果显示，PdCo纳米颗粒具有较小粒径(约4 nm)且成功地分散在HC上。PdCo/HC0.5700在碱性介质中电催化氧化甲醇时表现出优秀的电催化活性、稳定性和CO耐受性，这种显著的高性能可以归因于生物质载体大的表面积和Co的成功掺杂。关键词：花生壳；多孔碳；PdCo合金；甲醇电氧化中图分类号：O614.82+3；O614.81+2文献标识码：A文章编号：10014861(2023)10202013DOI：10.11862/CJIC.2023.157Peanut shellbased porous carbon supported PdCo catalystfor electrooxidation of methanol in alkaline mediaHUO ZhaoHui,1,2WEI XueRong1HUANG Yong1CHEN ZeYu1CHEN WeiBing1ZHANG QiTong1ZHANG Gang3WEN GengLong1SHI JunJie1(1School of Chemistry and Materials Science,Guangdong University of Education,Guangzhou 510303,China)(2Engineering Technology Development Center of Advanced Materials&Energy Savingand Emission Reduction in Guangdong Colleges and Universities,Guangzhou 510303,China)(3Shenzhen Fangrun Environmental Technology Co.,Ltd.,Shenzhen,Guangdong 518107,China)Abstract:Peanut shells were used as raw materials and activated to peanut shellbased porous carbon(HC)byKOH.Nitrogen adsorptiondesorption studies showed that the obtained porous carbon featured a total surface areaas high as 1 645 m2g-1.PdCo/HC catalyst was prepared by the impregnation reduction method,in which HC wasthe carrier.Xray diffraction(XRD)and Xray photoelectron spectroscopy(XPS)analysis demonstrated that Co inthe catalyst was mainly in the form of Co and CoO,and Co was entered into the crystal lattice of Pd and formed a PdCoalloy.The TEM image of PdCo/HC0.5700 showed that numerous PdCo nanoparticles were successfully dispersedin the prepared porous carbon with a small particle size(ca.4 nm).PdCo/HC0.5700 exhibited apparent electrocatalytic activity,CO tolerance,and stability towards methanol electrooxidation in alkaline media.This remarkable highperformance can be attributed to the large surface area of the biomass carrier and the doping of Co into Pd.Keywords:peanut shell;porous carbon;PdCo alloy;methanol electrooxidation第10期0IntroductionBiomass is the most widely existing material onthe earth,and all recyclable organic materials belongto biomass.In recent years,the preparation of newfunctional materials using biomass as raw materialshad been a research hotspot,and biomassbasedporous carbon is one of them15.For example,Yu et al.6prepared a Coloaded Ndoped biochar electrocatalystfrom sawdust,which exhibited excellent oxygen reduction reaction activity,higher stability(the currentremained at 98.1%after running for 10 000 s),andmethanol tolerance(the current remained 96.5%afteradding methanol)than Pt/C.Rupa et al.7fabricated Ptdecorated Artocarpus heterophyllous seedderived carbon as an anode catalyst for direct methanol fuel cell(DMFC)application.The prepared Pt/C showed excellent electrocatalytic activity in the potential range ofinterest with a high electrochemical active surface area(ECSA)of 261.4 m2g-1.The advantages of using thelisted above hydro charderived carbonbased materials as a supported catalyst are lightweight,plentiful,cheap,porous,effective,nontoxic,and heat resistant,and they have a high surface area and a versatilenature.Peanut shells as a kind of agricultural waste biomass,and their production is huge but only a little partof them were used to grow edible fungus,such as livestockfeed,refinedprocessing,supplyexceededdemand,making the most of peanut shells became useless.Most of them were burned as waste or discardedas garbage,which constituted a burden on the environment.Therefore,it was necessary to exploit more applications of them.However,in todays reports on peanutshellbased porous carbon,it is often applied in pollutant degradation or supercapacitor electrode materials811.However,there are rare reports on peanut shellsas the carrier material of DMFC anode catalyst.Thepeanut shells had a natural hole structure.KOH etching can further enrich its pore structure and make ithave a high specific surface area and pore volume12.Itwas believed that it is a potential DMFC anode catalystcarrier,which can be good for loading the active components in the catalyst.Currently,most of the anode catalysts for directmethanol fuel cells is Ptbased catalysts1318.However,Pt is more abundant in natural reservations.Therefore,people begin to pay attention to Pdbased catalysts1920.Wang et al.21prepared a PdAg/C catalyst by reducingPd(NO3)2xH2O and AgNO3with NaBH4,using carbonblack as the carrier,which showed better electrocatalytic activity and antiCO toxicity ability than Pd/C catalyst in alkaline methanol solution.Qiu et al.22prepared Pd and PdNi bimetallic catalysts,which loadedon carbon black using formic acid reduction.The average particle size was between 210 nm and PdNi/Chad higher catalytic activity for electrooxidation ofmethanol than Pd/C,indicating that Pd Ni/C had apotential application in lowcost alkaline fuel cells.Inaddition to being cheaper than Ptbased catalysts,Pdbased catalysts were also competitive in electrocatalytic activity and antiCO oxidization properties in alkaline media2123.Recent research shows that doping nonprecious metal Co in a palladiumbased catalyst couldeffectively improve its electrochemical activity and stability2427.For instance,Zhang et al.28synthesized thecatalyst for PdCo hybrid particles by twostep electrodeposition and templatefree GRR(graphene randomresistor)deposition in the templatebased diethyl carbonate improving the methanol oxidation reaction catalytic performance.Considering with the addition of Co can enhancethe stability,electrocatalytic oxidation activity,and antiCO toxicity ability of the Pdbased catalyst,and thepeanut shell porous carbon(HC)obtained by chemicalactivation had a good pore structure29,we prepared HCby the KOH activation method and then decorated PdCo nanoparticles to produce a DMFC anode catalystwith a low price and good electrocatalytic performance.1Experimental1.1Materials and methods1.1.1MaterialsPeanut shell was purchased in the market.KOHwas purchased from Tianjin Damao Chemical ReagentCo.,Ltd.CoCl26H2O and NaOH were purchased fromShanghai Aladdin Reagent Co.,Ltd.NaBH4was pur霍朝晖等：花生壳基多孔碳负载PdCo催化剂应用于碱性介质中电氧化甲醇2021无机化学学报第39卷chased from Shandong Xiya Chemical Co.,Ltd.HCl(37%)waspurchasedfromGuangzhouChemicalReagent Co.,Ltd.PdCl2(Pd content was above 60%)was purchased from Shandong Xiya Chemical Co.,Ltd.All reagents were analytical grade and used without further purification.1.1.2Synthesis of HC4.0 g of cleaned,dried,crushed,and sieved peanut shell powder were placed into four beakers andadded with flake KOH activator(The mass ratio ofactivator KOH to peanut shell powder was 0.5 1,1 1,2 1,3 1,respectively).Then,30 mL of distilled waterwas added and thoroughly stirred,followed by soakingfor 12 h.After 12 h of immersion with a filter,the liquid was taken out from the sample,and then the sample was dried for 12 h in an 80 oven to remove theremaining water and completely dry the sample.Thedried sample was transferred to a crucible.Under anitrogen environment,the sample was carbonized at300 with a heating rate of 5 min-1for 1 h.It wasthen further carbonized at high temperatures(600,700,800,and 900)for 1.5 h with a heating rate of 3 min-1.The muffle furnace was allowed to cool to roomtemperature,and then the carbonized sample was taken out.The obtained sample was immersed in 1 molL-1hydrochloric acid for 12 h.After washing with distilled water to neutrality,it was dried at 80 for 12 hto obtain HCxT,where x represented the proportion ofactivator and T represented the activation temperature).HC0T represented the nonactivated HC.1.1.3Synthesis of catalysts20 mg HC was put into a beaker and 20 mL of isopropanolwater solution(volume ratio of 2 1),1.58 mLof 0.03 molL-1PdCl2solution,and 4.1 mg of CoCl26H2O were added,then the beaker with the solutionwas ultrasonically vibrated for 30 min.After this,theuniform solution was placed in a water bath.When itwas heated to 70,1.0 molL-1NaOH solution wasadded under continuous stirring to adjust the pH to10.0.Then slowly added the excess mass fraction of5%NaBH4solution into the solution by dropwise andstirred it magnetically in a water bath at 70 for 3 h.After the reaction,the product was washed and filteredmany times with ultrapure water to remove unnecessarysalt and reductant.Then the sample was dried in thevacuum drying oven at 120 for 6 h and the PdCobinary catalyst was obtained.The theoretical palladiumand cobalt loading(mass fraction)of the catalyst were20%and 4%,and the catalyst was denoted as PdCo/HCxT.Pd/HCxT and Co/HCxT were prepared by thesame method,except for the addition of CoCl26H2O orPdCl2.1.1.4Structure and morphology characterizationsIRIS Advantage inductively coupled plasma atomic emission spectroscopy(ICPAES)system(Thermo,America)was used to detect Pd and Co compositions ofPd Co/HC catalysts.The emission lines were Pd=340.458 nm and Co=228.616 nm.The crystal structureand the chemical compositions of the catalysts weredetermined by using Xray diffraction(XRD,workingvoltage of 40 V,working current of 25 A)analysis.Thediffraction patterns of experimental catalysts were measured with a commercial diffractometer(Bruker D8,Germany)with a Cu K radiation source,=0.154 18nm,at a scan rate of 3()min-1in a 2 range from 10to 90.The structure and morphology of the materialswere carried out by scanning electron microscopy(SEM,TESCAN MIRA 3 LMU,accelerating voltage 15kV).The particle size and morphology of the Pd/HCand PdCo/HC were analysed by transmission electronmicroscopy(TEM,JEM2100HR,Japan,acceleratingvoltage of 200 kV).For TEM characterization,the catalyst powders were ultrasonically dispersed in an ethanol solution to get uniform catalyst ink.After that,thecatalyst ink was transferred onto copper grids coveredwith holey carbon film and dried in the air.The conductivity of HC was tested by the fourprobe method(ShenzhenCrystalLatticeElectronicsCo.,Ltd.ST2742B automated powder tester).Using an automaticspecific surface adsorption instrument(5.0.0.3 Belsorp,BEL Japan,Inc.Instrument),the N2adsorptionisotherms were measured at-196,and the sampleswere outgassed at 180 for 12 h before measurements.The specific surface area and the pore size distributions were obtained from the desorption branch ofthe isotherms by using the Brunauer Emmett Teller2022第10期(BET)method and BarrettJoynerHalenda(BJH)analyses,respectively.The Xray photoelectron spectroscopy(XPS)spectra were measured by a commerciallyavailable analyzer(Thermo ESCALAB 250XI,testenergy 1 486.6 eV)and were used to analyze the compositions of samples.1.1.5Electrochemical measurementsA CS electrochemical workstation(A4602,WuhanKesite Instrument Co.,Ltd.)was performed using athree electrode system which was prepared by dropping 20 mL catalyst sample(ultrasonic mixing 2.0 mgelectrocatalyst and 100 mL absolute ethanol)on aclean glassy carbon(GC)electrode,a platinum electrode,and a saturated Ag/AgCl electrode(3 molL-1NaCl)as the working,counter,and reference electrodes,respectively.Cyclic voltammetry(CV)was performed in N2saturated 0.5 molL-1NaOH solution or0.5 molL-1NaOH and 1 molL-1CH3OH solution atroom temperature.Chronoamperometry(CA)was measured in N2saturated 0.5 molL-1NaOH and 1 molL-1CH3OH solution at room temperature and the potentialwas 1.0 V(vs NHE).2Results and discussion2.1Characterization of HCFig.1a shows the XRD patterns of HC prepared at800 with different dosages of activators.The XRDpatterns of biomass carbon prepared at the five different dosages of activators were very similar.The twowide characteristic peaks at near 2=24.0 and 43.5represented the(002)and(100)surface of graphite,respectively.The appearance of these two peaks indicated that the HC was amorphous26.By comparison,with the increase of activator,the above two characteristic peaks became gradually weak.The peak of HC0800 without an activator was the highest,which indicated that the activator KOH could corrode and destroythe material structure.With the increase of the dosageof the activator,the etching of KOH on the structure ofHC was strengthened,which made the confusiondegree of the sample structure increase and the graphitization degree decrease.Withtheincreaseofactivationtemperature(Fig.1b),the above two characteristic peaks graduallybecame wide and weak.This was because the activatorKOH could etch and destroy the material structure,and with an increase in the amount of activator,thedamage to the porous structure of the peanut shell based carbon by KOH was intensified,leading to anincreased degree of disorder in the sample structureand a reduced degree of graphitization.Fig.2a2e are the SEM images of HC prepared at800 with different dosages of activator.Fig.2a represents HC0800,which is the sample prepared withoutadding KOH for activation.Its holes were rare and thesurface of the hole was relatively flat.Compared withother samples,we could find that with the KOH activator,the structure of the samples was etched,and thesurface appeared many folds.According to the SEMimages,HC0.5800 had the most abundant hole strucFig.1XRD patterns of(a)HCx800 and(b)HC0.5T霍朝晖等：花生壳基多孔碳负载PdCo催化剂应用于碱性介质中电氧化甲醇2023无机化学学报第39卷ture.As the ratio of alkali to material increased,thesamples aperture was bigger as well as the holedecreased,since the more amount of KOH,the strongerthe etching ability of the sample.Excessive etching ledto the collapse of the pore structure of the sample.Fig.2f2h are the SEM images of HC prepared atdifferent activation temperatures,and the ratio of alkalito the material was 1.As shown in these figures,HC1600 had only a few small holes and was not fullyetched.HC1700 had the most abundant pore structure.Starting from HC1800,the holes began to decrease,and the aperture became large.It indicated that theactivation ability of the KOH activator to HC increasedwith the increase of temperature,but when the temperature was too high,the activation ability was too strong,and the sample was excessively corroded,which led tothe collapse of pore structure and the decrease of thehole and the increase of aperture.Fig.3a was the adsorptiondesorption isotherms ofHC prepared with different contents of activator in liquid nitrogen at 77 K.When the relative pressure p/p00.1,the nitrogen adsorption capacity of the five samples increased rapidly.According to the IUPAC classification of physical sorption isotherm,this is the characteristics of type curve,which represents the existence of the microporous structure.For HC0.5800 in relative pressure p/p00.1,the nitrogen adsorption was saturated and a