Noble metal-free bifunctional oxygen evolution and oxygen reduction ...

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Supplementary information

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Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-

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catalysts

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Prasad Prakash Patel1, Moni Kanchan Datta2,3, Oleg I. Velikokhatnyi2,3, Ramalinga Kuruba2,

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Krishnan Damodaran4, Prashanth Jampani2, Bharat Gattu1, Pavithra Murugavel Shanthi1, Sameer

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S. Damle1, Prashant N. Kumta1,2,3,5,6*

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of Pittsburgh, Pittsburgh, PA 15261, USA.

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Department of Chemical and Petroleum Engineering, Swanson School of Engineering, University

Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh,

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Pittsburgh, PA 15261, USA.

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USA.

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Department of Chemistry, University of Pittsburgh, PA 15260

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Mechanical Engineering and Materials Science, Swanson School of Engineering, University of

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Pittsburgh, Pittsburgh, PA 15261, USA.

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School of Dental Medicine, University of Pittsburgh, PA 15217, USA.

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*

Corresponding author: Prof. Prashant N. Kumta ([email protected])

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Department of Bioengineering, 815C Benedum Hall, 3700 O’Hara Street, Pittsburgh, PA 15261.

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Tel: +1-412-648-0223, Fax: +1-412-624-3699

Center for Complex Engineered Multifunctional Materials, University of Pittsburgh, PA 15261,

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Table of contents:

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Section S1: Methanol tolerance test of Cu1.5Mn1.5O4:10F and Pt/C

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Section S2: Synthesis of Cu1.5Mn1.5O4:10F via ball-milling

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Figure S1. SEM micrograph with elemental x-ray maps of Cu1.5Mn1.5O4:10F

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Figure S2. EDX spectrum of Cu1.5Mn1.5O4:10F

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Figure S3. HRTEM image showing lattice fringes with spacing of ~0.249 nm corresponding to

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the (113) interplanar spacing of cubic Cu1.5Mn1.5O4:10F

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Figure S4. The XPS spectra of Cu1.5Mn1.5O4 and Cu1.5Mn1.5O4:10F showing Cu 2p3/2 peak

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Figure S5. The XPS spectra of Cu1.5Mn1.5O4 and Cu1.5Mn1.5O4:10F showing Mn 2p3/2 peak

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Figure S6. 19F MAS NMR spectra of Cu1.5Mn1.5O4:5F, Cu1.5Mn1.5O4:10F, Cu1.5Mn1.5O4:15F and

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Cu1.5Mn1.5O4:20F; spinning side bands are marked by asterisks

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Figure S7. The Tafel plot (for OER) after iR correction of Cu1.5Mn1.5O4

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Figure S8. The Tafel plot (for OER) after iR correction of Cu1.5Mn1.5O4:5F

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Figure S11. The polarization curve of chemically synthesized and ball-milled Cu1.5Mn1.5O4:10F

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using total loading of 1 mg/cm2 and in-house synthesized IrO2 using total loading of 0.15 mg/cm2

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obtained in 0.5 M H2SO4 solution at 400C with a scan rate of 5 mV/sec after iRΩ correction

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Figure S12. Galvanostatic (constant current) measurement of electrochemical activity of

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chemically synthesized and ball milled Cu1.5Mn1.5O4:10F (total loading1 mg/cm2) and in-house

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synthesized IrO2 (total loading0.15 mg/cm2) performed in 0.5 M H2SO4 electrolyte solution at

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400C at a constant current of 2 mA/cm2

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Figure S13. The Tafel plot (for ORR) after iR correction of Cu1.5Mn1.5O4, Cu1.5Mn1.5O4:5F,

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Cu1.5Mn1.5O4:10F and Cu1.5Mn1.5O4:15F

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Figure S14. The polarization curve for ORR of Cu1.5Mn1.5O4:10F (total loading  50 g/cm2) at

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different rotation speeds measured in O2-saturated 0.5 M H2SO4 solution at 260C with a scan rate

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of 5 mV/sec

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Figure S15. The Koutechy-Levich plot for ORR of Cu1.5Mn1.5O4:10F at 0.6 V (vs RHE)

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Figure S16. The polarization curve of Cu1.5Mn1.5O4:10F obtained in O2-saturated 0.5 M H2SO4

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solution at 260C with rotation speed of 2500 rpm and scan rate of 5 mV/sec after iRΩ correction

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using total loading of 50 g/cm2, with and without 1 M methanol in 0.5 M H2SO4 electrolyte

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solution

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Figure S17. The polarization curves of Pt/C obtained in O2-saturated 0.5 M H2SO4 solution at

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260C with rotation speed of 2500 rpm and scan rate of 5 mV/sec after iRΩ correction using Pt

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loading of 30 gPt/cm2 for Pt/C, with and without 1 M methanol in 0.5 M H2SO4 electrolyte solution

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Figure S18. The polarization curves of chemically synthesized and ball-milled Cu1.5Mn1.5O4:10F

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and Pt/C obtained in O2-saturated 0.5 M H2SO4 solution at 260C with rotation speed of 2500 rpm

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and scan rate of 5 mV/sec after iRΩ correction using total loading of 50 g/cm2 for

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Cu1.5Mn1.5O4:10F and Pt loading of 30 gPt/cm2 for Pt/C

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Figure S19. The iRΩ corrected polarization curve of Cu1.5Mn1.5O4:10F (total loading  1 mg/cm2)

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obtained after 24 h of chronoamperometry test in 0.5 M H2SO4 solution at 400C with a scan rate

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of 5 mV/sec

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Figure S20. Theoretical and experimentally measured concentration of O2 gas, measured (for 6 h)

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during chronoamperometry test of Cu1.5Mn1.5O4:10F (total loading1 mg/cm2), performed in 0.5

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M H2SO4 solution under a constant potential of 1.55 V (vs RHE) at 400C

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Figure S21. The cyclic voltammogram (CV) of Cu1.5Mn1.5O4:10F measured in N2 saturated 0.5 M

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H2SO4 at 260C at scan rate of 5 mV/sec using total loading of 50 g/cm2, initial and after 6000

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cycles

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Section S1: Methanol tolerance test:

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In DMFCs, methanol cross-over from anode to cathode has detrimental effect on the fuel cell

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performance due to the undesired reaction with O2 and cathode electro-catalyst.1 Hence, methanol

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tolerance of Cu1.5Mn1.5O4:10F is studied by conducting polarization studies in O2-saturated (1 M

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methanol + 0.5 M H2SO4) electrolyte solution at 260C using a scan rate of 5 mV/sec and rotation

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speed of 2500 rpm employing a total loading of 50 g/cm2 for Cu1.5Mn1.5O4:F. For comparison,

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methanol tolerance of commercial Pt/C is also studied with Pt loading of 30 gPt/cm2 under

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identical operating conditions. The polarization curves of Cu1.5Mn1.5O4:10F and Pt/C with and

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without presence of methanol in 0.5 M H2SO4 electrolyte solution are shown in the

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Supplementary Figs. S17-S18, respectively. The significant increase in overpotential (400 mV)

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in methanol containing electrolyte solution is observed for Pt/C (Supplementary Fig. S18) mainly

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due to the competition between ORR and methanol electro-oxidation, which is similar to that

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reported earlier.2 However, only a minimal increase in overpotential (7 mV) is seen for

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Cu1.5Mn1.5O4:10F in methanol containing electrolyte solution (Supplementary Fig. S17)

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suggesting the excellent methanol tolerance of the oxide electro-catalyst which is significantly

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superior to Pt/C. Hence, we believe Cu1.5Mn1.5O4:10F is indeed a promising cathode electro-

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catalyst for ORR in DMFCs.

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Section S2: Synthesis of Cu1.5Mn1.5O4:10F via ball-milling:

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Mixtures of CuO (Alfa Aesar, 99.5%),MnO (Alfa Aesar, 99.5%) and (NH4F, 98%, Alfa Aesar)

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corresponding to the stoichiometric composition were subjected to high energy mechanical milling

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in a high energy shaker mill for 5 h in a stainless steel (SS) vial using 20 SS balls of 2 mm diameter

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with a ball to powder weight ratio 10:1. The milled powder was then heat treated in air at 5000C

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for 4 h (Ramp rate=100C/min).

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Figure S1. SEM micrograph with elemental x-ray maps of Cu1.5Mn1.5O4:10F

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Figure S2. EDX spectrum of Cu1.5Mn1.5O4:10F

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Figure S3. HRTEM image showing lattice fringes with spacing of ~0.249 nm corresponding to

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the (113) interplanar spacing of cubic Cu1.5Mn1.5O4:10F

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Figure S4. The XPS spectra of Cu1.5Mn1.5O4 and Cu1.5Mn1.5O4:10F showing Cu 2p3/2 peak

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Figure S5. The XPS spectra of Cu1.5Mn1.5O4 and Cu1.5Mn1.5O4:10F showing Mn 2p3/2 peak

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Figure S6. 19F MAS NMR spectra of Cu1.5Mn1.5O4:5F, Cu1.5Mn1.5O4:10F, Cu1.5Mn1.5O4:15F and

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Cu1.5Mn1.5O4:20F; spinning side bands are marked by asterisks

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Figure S7. The Tafel plot (for OER) after iR correction of Cu1.5Mn1.5O4

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Figure S11. The polarization curve of chemically synthesized and ball-milled Cu1.5Mn1.5O4:10F

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using total loading of 1 mg/cm2 and in-house synthesized IrO2 using total loading of 0.15

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mg/cm2 obtained in 0.5 M H2SO4 solution at 400C with a scan rate of 5 mV/sec after iRΩ

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correction

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Figure S12. Galvanostatic (constant current) measurement of electrochemical activity of

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chemically synthesized and ball milled Cu1.5Mn1.5O4:10F (total loading1 mg/cm2) and in-house

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synthesized IrO2 (total loading0.15 mg/cm2) performed in 0.5 M H2SO4 electrolyte solution at

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400C at a constant current of 2 mA/cm2

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Figure S13. The Tafel plot (for ORR) after iR correction of Cu1.5Mn1.5O4, Cu1.5Mn1.5O4:5F,

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Cu1.5Mn1.5O4:10F and Cu1.5Mn1.5O4:15F

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Figure S14. The polarization curve for ORR of Cu1.5Mn1.5O4:10F (total loading  50 g/cm2) at

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different rotation speeds measured in O2-saturated 0.5 M H2SO4 solution at 260C with a scan rate

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of 5 mV/sec

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Figure S15. The Koutechy-Levich plot for ORR of Cu1.5Mn1.5O4:10F at 0.6 V (vs RHE)

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Figure S16. The polarization curve of Cu1.5Mn1.5O4:10F obtained in O2-saturated 0.5 M H2SO4

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solution at 260C with rotation speed of 2500 rpm and scan rate of 5 mV/sec after iRΩ correction

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using total loading of 50 g/cm2, with and without 1 M methanol in 0.5 M H2SO4 electrolyte

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solution

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Figure S17. The polarization curves of Pt/C obtained in O2-saturated 0.5 M H2SO4 solution at

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260C with rotation speed of 2500 rpm and scan rate of 5 mV/sec after iRΩ correction using Pt

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loading of 30 gPt/cm2 for Pt/C, with and without 1 M methanol in 0.5 M H2SO4 electrolyte

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solution

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Figure S18. The polarization curves of chemically synthesized and ball-milled Cu1.5Mn1.5O4:10F

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and Pt/C obtained in O2-saturated 0.5 M H2SO4 solution at 260C with rotation speed of 2500 rpm

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and scan rate of 5 mV/sec after iRΩ correction using total loading of 50 g/cm2 for

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Cu1.5Mn1.5O4:10F and Pt loading of 30 gPt/cm2 for Pt/C

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Figure S19. The iRΩ corrected polarization curve of Cu1.5Mn1.5O4:10F (total loading  1

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mg/cm2) obtained after 24 h of chronoamperometry test in 0.5 M H2SO4 solution at 400C with a

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scan rate of 5 mV/sec

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Figure S20. Theoretical and experimentally measured concentration of O2 gas, measured (for 6

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h) during chronoamperometry test of Cu1.5Mn1.5O4:10F (total loading1 mg/cm2), performed in

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0.5 M H2SO4 solution under a constant potential of 1.55 V (vs RHE) at 400C

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Figure S21. The cyclic voltammogram (CV) of Cu1.5Mn1.5O4:10F measured in N2 saturated 0.5

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M H2SO4 at 260C at scan rate of 5 mV/sec using total loading of 50 g/cm2, initial and after 6000

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cycles

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References:

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1.

Lee K, Zhang L, Zhang J. Ir x Co 1− x (x= 0.3–1.0) alloy electrocatalysts, catalytic activities, and methanol tolerance in oxygen reduction reaction. Journal of Power Sources 170, 291-296 (2007).

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Wang D, et al. Facile Synthesis of Carbon-Supported Pd–Co Core–Shell Nanoparticles as Oxygen Reduction Electrocatalysts and Their Enhanced Activity and Stability with Monolayer Pt Decoration. Chemistry of Materials 24, 2274-2281 (2012).

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