电化学试验报告试验报告

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Experimentalclasson“FuelCellandElectrochemistry〞

Experimentsetup

Equipment:CHI760Delectrochemicalstation

Threeelectrodesystem.WE:CE:RE:SaturatedCalomelElectrodeSolution:1.010-3mol/LK3[Fe(CN)6]+0.1MKCl

Labreport

1)PlotcurvesofLSVcurve,anddescribewhycurrentchangeswithsweepingvoltage?

0.000010

0.000008

0.000006

Current/uA

0.000004

0.000002

0.000000

0.6

0.4

0.2

0.0

-0.2

-0.4

Potential/V

oltageisadrivingforcetoanelectrodereactions,itisconcernedwiththeequilibrium

ofelectrontransferatelectrodesurface.Asthealteringofappliedvoltage,theFermi-levelisraised(orlowered),whichchangingtheenergystateoftheelectrons.Makingtheoverallbarrierheight(ieactivationenergy)alterasafunctionoftheappliedvoltage.

(1).Inthisreaction,whenvoltageis0.6V,thereisnoelectrontransfer,sothecurrentiszero.

Withthevoltagetothemorereductivevalues,thecurrentincreases.

(2).WhenthediffusionlayerhasgrownsufficientlyabovetheelectrodesothatthefluxofreactanttotheelectrodeisnotfastenoughtosatisfythatrequiredbyNernstEquation.Thepeakisobtaining.(3).Whenthereactioncontinued,itwouldgetasituationthattherewillbealowerreactantconcentrationattheelectrodethaninbulksolution,thatis,thesupplyoffreshreactanttothesurfacedecreased,socurrentdecreases.

2)PlotthecurvesofCVcurveswithdifferentscanrate;

Current/A

0.6

0.4

0.2

0.0

-0.2

-0.4

Potential/V

3)FromtheCVcurves,fillthetable

4)Accordingtotheresult,describewhycurvesshowscertaintrend,andhowpeakcurrent

andpeakvoltagedifferencechangewithscanrate?

Fromabovedataandcurve,wecanobtain:

A.Atafixedscanrate:(1).frominitialpositivevoltagetomorereductivevalues,thecurrentbegin

toflow,thenreachapeakipcanddecreaseeventually.(2).whenvoltagemovesback,the

2+3+

equilibriumpositionsgraduallyconvertingelectrolysisproduct(Fe)backtoreactant(Fe),thecurrentflowisfromthesolutionspeciesbacktotheelectrodeandsooccursintheopposite

sensetotheforward.Theprocesshasanothercurrentpeakipa.Ithassamereasonoflinearsweepvoltammetry.

B.Atdifferentscanrate,theratioofpeakcurrentipc/ipaisaboutequalto1(1.009—1.043).C.Atdifferentscanrate,thepositionofpeakvoltagedonotaltergreatlyΔEpisabouta

constant(66--79).

(1)Ip--V1/2

50

40

30

Ip/uA

2023

51015202530

v1/2/(mV/s)1/2

Figure1:PeakcurrentVSradicalsignofscanrate

Itisapparentthatthepeakcurrentislineartoradicalsignofscanrate,which

1/2

satisfythisequation:ip=kvC0.

Reason:Thiscanberationalisedbyconsideringthesizeofthediffusionlayerandthetimetakentorecordthescan.Clearlythelinearsweepvoltammogramwilltakelongertorecordasthescanrateisdecreased.Thereforethesizeofthediffusionlayerabovetheelectrodesurfacewillbedifferentdependinguponthevoltagescanrateused.Inaslowvoltagescanthediffusionlayerwillgrowmuchfurtherfromtheelectrodeincomparisontoafastscan.Consequentlythefluxtotheelectrodesurfaceisconsiderablysmalleratslowscanratesthanitisatfasterrates.Asthecurrentis

proportionaltothefluxtowardstheelectrode,themagnitudeofthecurrentwillbeloweratslowscanratesandhigherathighrates.

(2)Ep--V

(3)Ep’--v

)

V(pE0100202300400500600700

v(mV/s)

Figure2:PeakpotentialVSscanrate

160

120

Ep'(mV)

80

40

0v(mV/s)

Figure3:thechangeofPeakpotentialVSscanrate

Figure3:showsthePeakvoltagedifferenceiscons