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P1-946Toward OperandoObservation of Active Site Dynamics in Oxygen Evolution Catalysts by Lab-Scale Near-Ambient Pressure XPSKey Words: Water Electrolysis, NAP-XPS, OperandomeasurementProtonExchangeMembraneWaterElectrolysis(PEMWE)hasattractedmuchattentionasakeytechnologyforproducinggreenhydrogentobuildacarbon-neutralsociety.However,itsdeploymentisseverelylimitedbythesluggishkineticsandlargeoverpotentialofOxygenEvolutionReaction(OER)attheanode.Therefore,thedevelopmentofhighlyactiveanddurablecatalystsisurgentlyneeded.⚫NAP-XPSisapowerfultechniqueforinvestigatingelectrochemicalreactionmechanismsatthesolid-aqueousinterfacebecauseitprovidebothhigh,element-specificsurfacesensitivityandtooperateatpressuresabovewater’svaporpressure.⚫Wewereabletomeasureliquidwaterwithinminutes.ConclusionSPECS EnviroESCAExperiment setup⚫Wewillconstructasystemthatallowsforbothelectrochemicalmeasurementsandacontrollablewatersupplytoobservespectralchangesofthecatalystsandinterfacialwater.Future PlanIntroductionOperandoanalysisisapowerfulapproachforelucidatingthecatalyticreactionmechanismforthedevelopmentofhighlyactiveanddurablecatalysts.Therefore,weaimtoimplementoperandoelectrochemicalXPSbyintegratinganovel,custom-designedoperandocellwithalab-scaleNAP-XPSinstrument.Thiswillenableustomonitortheelement-selectivebehaviorduringthecatalyticreactionandultimatelyclarifyitsunderlyingmechanism.Theme underDiscussionBattery Materials Analysis Group, GREEN Hisao KiuchiE-mail：： KIUCHI.Hisao@nims.go.jp⚫X-ray source: Al K(hv = 1486.6 eV)⚫Measurement pressure: Up to ~0.1 atom⚫Spot size: 300 μm⚫Energy resolution: 0.5 ~ 1.0 eVP. M. Dietrich et al., Surf. Sci. Spectra 32, 013001 (2025).O 1sXPS spectrum of gas and liquid H2OPropose reaction mechanismAl KX-raysPhotoelectronsX-ray AnodeSampleFocusing MirrorElectron PathElectron DetectorElectron AnalyzerX-ray BeamX-ray SourceHigh, element-specific surface sensitivity at 0.1 atom !!Very stable and quick measurementsOperandomeasurement under electrochemical reaction