Effect of ordering of PtCu3 electrocatalyst structure on the stability for oxygen reduction reaction

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Effect of ordering of PtCu3 electrocatalyst structure on the stability for oxygen reduction reaction

Nejc Hodnik1,2, C. Jeyabharathi1,3, K. Phani3, A. Renik4, M. Bele2, S. Hoevar2, M. Gaberek2 and K. Mayrhofer1

1Max-Planck-Institut fr Eisenforschung GmbH, Dsseldorf, GermanyDepartment of Interface Chemistry and Surface EngineeringElectrocatalysis Group2National Institute of Chemistry, Ljubljana, Slovenia3CSIR-Central Electrochemical Research Institute, Tamil Nadu, India4Joef Stefan Institute, Ljubljana, Slovenia

10thEuropean Symposium on Electrochemical Engineering, Sardinia, Italy /#

Effect of ordering of PtCu3 electrocatalyst structure on the stability for oxygen reduction reactionLike Pt-based nanoparticles on high surface carbon.

Membrane

AnodeCathodeElectrocatalyst requires improvement of performance & stability = cost !Key parameters for expensive catalytic nanoparticlesIntroduction Monolayer concept PtCu3 nanoparticles Microscopy

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ESA electrochemical surface areaS/m = [m2Pt/gPt]

S = 4r2m= (4/3)r3 S/m=k*1/rjm mass activityI/m = [A/mgPt]

I = kSce-kEm= (4/3)r3 jk specific activityI/S = [mA/cm2Pt]I = kSce-kES = 4r2Key parameters for expensive catalytic nanoparticlesThe activity:

X

= jm = ESA * jk

Introduction Monolayer concept PtCu3 nanoparticles Microscopy

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Core-shell particles have by default larger ESA

Monolayer type ESA = constant = 152 m2/gPtMonolayer concept: Increasing ESA

PtCu

Interestingy, here ESA is particel size independent! Unlike the activity!Introduction Monolayer concept PtCu3 nanoparticles MicroscopySounds much like Pt-monolayer concept of Prof. Adzic group and Pt-skin of Prof. Markovic group. jm = ESA * jk

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Potential advantages reached besides high ESA are enhanced specific activity due to altered Pt electrochemical adsorptive properties:

1.Particle size effect2. Shape effect3.Ligand effect4.Strain effect5.Proximity effect6.Nano-confidement effect...

x.Effect od structural ordering

PtCu

Monolayer concept: Increasing jkSounds much like Pt-monolayer concept of Prof. Adzic group and Pt-skin of Prof. Markovic group.Introduction Monolayer concept PtCu3 nanoparticles Microscopy jm = ESA * jk

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Effect of ordering of PtCu3 electrocatalyst structure on the stability for oxygen reduction reactionReal model system: PtCu3 nanoparticles on C

0,0250,015

1,001,330,330,671,672,002,33Introduction Monolayer concept PtCu3 nanoparticles Microscopy

jm = ESA * jk

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Real model system: PtCu3 nanoparticles on C


1. Partially Ordered samples:Annealing 15 min at 750 C followed by 1 hour at 500 C in reductive atmosphere

2. Disordered sample: Heating the ordered sample to 700 C with subsequent quenching in liquid nitrogen

500C disorderorder transition temperature

Both samples are embedded on a graphitic carbon support with identical initial composition, particle dispersion and size distribution, yet with different degrees of structural ordering.

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Introduction Monolayer concept PtCu3 nanoparticles MicroscopyPtCu3 nanoparticles dealloying and activityRregardless of the degradation/dealloying treatment, the partially ordered structure contains significantly higher (2030%) specific activity compared to the fully disordered sample.

See Nejc Hodnik, Miran Gaberek,Karl J. J. Mayrhofer et al.,Phys. Chem. Chem. Phys.2014, 16, 13610.See Marjan Bele, Nejc Hodnik and Miran Gaberek et al.,Chem. Comm.2014, :DOI:10.1039/c4cc05637j.

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Effect of ordering of PtCu3 electrocatalyst structure on the stability for oxygen reduction reactionPlatinum dissolution: PtCu3 nanoparticlesIntroduction Monolayer concept PtCu3 nanoparticles MicroscopyDissolution of Platinum: Limits for the Deployment of Electrochemical Energy Conversion?**Angel A. Topalov and Karl J. J. MayrhoferAngew. Chem. Int. Ed. 2012, 51, 12613 12615

ElectrolytesupplyCounter electrode

Electrolyteoutlet

Reference electrode

Silicon sealing

50-500mN

2mm

Working electrode

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Platinum dissolution: PtCu3 nanoparticlesIntroduction Monolayer concept PtCu3 nanoparticles MicroscopyHow to decide if one has an opportunity to choose between high ESA and low SA or low ESA and high SA?New Insight into Platinum Dissolution from Nanoparticulate Platinum-Based Electrocatalysts Using Highly Sensitive In Situ Concentration MeasurementsJovanovic P., Hodnik N. and M Gaberscek. CHEMCATCHEM, 2014, vol. 6, i. 2, pp. 449-453.

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20 nmIntroduction Monolayer concept PtCu3 nanoparticles MicroscopyIdentical location TEM of PtCu3 nanoparticles

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Effect of ordering of PtCu3 electrocatalyst structure on the stability for oxygen reduction reaction- dealloying: 500 + 6500 cycles in 0,1 M HClO4Introduction Monolayer concept PtCu3 nanoparticles MicroscopyIdentical location SEM of PtCu3 nanoparticles0.6 1.2 V

20 nm

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First try with in-situ electrochemical TEMDealloying of PtCu3 with cycling:- pores formation- beam induced (radiolysis) dynamic nanoscale Cu precipitationIntroduction Monolayer concept PtCu3 nanoparticles Microscopy100 nm

Protochips Poseidon 500

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Thank you for your attention!Introduction Monolayer concept PtCu3 nanoparticles Microscopy40 nm

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Introduction Monolayer concept PtCu3 nanoparticles Microscopy100 nm

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M. K. Debe, Nature, 2012, 486, 43-51.

Introduction Monolayer concept PtCu3 nanoparticles MicroscopyReal PtCu3 nanoparticles catalyst activity

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Pt-Cu -> Cu2+ (0,74V)


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Effect of ordering of PtCu3 electrocatalyst structure on the stability for oxygen reduction reaction- dealloying: 500 + 6500 cycles in 0,1 M HClO420 nm

Introduction Monolayer concept PtCu3 nanoparticles MicroscopyIdentical location SEM of PtCu3 nanoparticles20 nm

18zero cycles5,000 cycles50,000 cycles500 cycles0.6 1.2 V

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Science

Effect of ordering of PtCu3 electrocatalyst structure on the stability for oxygen reduction reaction