Fig. 2 Exchange current density of HOR/HER as a function of pH. (A to D) Exchange current densities (i0) of HOR/HER on (A) Pt/C, (B) Ir/C, (C) Pd/C, and (D) Rh/C as a function of the pH of electrolytes. HOR/HER polarization curves were measured using the RDE method in H2-saturated electrolytes at a scanning rate of 1 mV/s and a rotation speed of 1600 rpm at 293 K. Gray stars represent HOR/HER exchange current densities at 293 K estimated from the Arrhenius plot of Durst et al. (24), in which all activities were measured using an H2-pump configuration.
Fig. 3 Correlation between the exchange current density of HOR/HER and Hupd desorption peak potential. Exchange current densities of HOR/HER on Pt/C, Ir/C, Pd/C, and Rh/C as a function of the lowest underpotential-deposited hydrogen (Hupd) desorption peak potential (Epeak) from CVs. The gray dashed line represents linear fitting of all data points.
- Table 1 Summary of β and A.
β and A from fitting i0 to Epeak using the expression
, activation energy (Ea) measured using the RDE method in 0.1 M KOH from this work and an H2-pump configuration from the study of Durst et al. (24), difference in Hupd desorption peak potentials (ΔEpeak) in 0.1 M KOH and acid with pH 0, and βEa calculated as [Ea (0.1 M KOH) − Ea (H2 pump)]/FΔEpeak.Ea (kJ/mol) ΔEpeak (V) βEa β A 0.1 M KOH H2 pump (pH 0) (24) Pt/C 0.5 59 29.6 ± 0.4 16 ± 2 0.17 0.8 Ir/C 0.8 68 32.8 ± 0.4 19 ± 3 0.20 0.7 Pd/C 0.6 37 38.9 ± 3.0 31 ± 2 0.14 0.6 Rh/C 0.6 36 26.6 ± 0.7 28 ± 1 — —
Supplementary Materials
Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/3/e1501602/DC1
Derivation of relationship between i0 and Epeak
Cyclic voltammograms of Pt/C, Ir/C, Pd/C, and Rh/C at different pH values
CVs and HOR/HER polarization curves at different pH values
Cyclic voltammograms (CVs)
Correlation of exchange current densities with Epeak
Arrhenius plot
CO stripping in electrolytes with different pH values
Effect of anions on HOR/HER activities
TEM images of supported metal electrocatalysts
Procedure for calculating pH for buffer solutions and comparison between calculated and experimental values
HOR/HER polarization curves on Vulcan XC-72 in electrolytes with different pH values
Fig. S1. CVs of Pt/C, Ir/C, Pd/C, and Rh/C at different pH values.
Fig. S2. CVs and HOR/HER polarization curves at different pH values on Pt/C.
Fig. S3. CVs and HOR/HER polarization curves at different pH values on Ir/C.
Fig. S4. CVs and HOR/HER polarization curves at different pH values on Pd/C.
Fig. S5. CVs and HOR/HER polarization curves at different pH values on Rh/C.
Fig. S6. CVs of Pt/C, Ir/C, Pd/C, and Rh/C in 0.1 M KOH.
Fig. S7. Correlation of exchange current densities with Epeak.
Fig. S8. Arrhenius plots of HOR/HER activities.
Fig. S9. CO stripping profiles on Pt/C at different pH values.
Fig. S10. CO stripping profiles on Ir/C at different pH values.
Fig. S11. CO stripping profiles on Pd/C at different pH values.
Fig. S12. CO stripping profiles on Rh/C at different pH values.
Fig. S13. Effect of anions on HOR/HER activities.
Fig. S14. TEM images and histograms of Pt, Ir, Pd, and Rh/C.
Fig. S15. Comparison of calculated and electrochemically measured pH of the electrolytes.
Fig. S16. HOR/HER polarization curves on Vulcan XC-72.
Table S1. Particle size and surface area of Pt/C, Ir/C, Pd/C, and Rh/C.
Table S2. Effect of anions on Hupd peak potentials and HOR/HER exchange current densities.
Additional Files
Supplementary Materials
This PDF file includes:
- Derivation of relationship between i0 and Epeak
- Cyclic voltammograms of Pt/C, Ir/C, Pd/C, and Rh/C at different pH values
- CVs and HOR/HER polarization curves at different pH values
- Cyclic voltammograms (CVs)
- Correlation of exchange current densities with Epeak
- Arrhenius plot
- CO stripping in electrolytes with different pH values
- Effect of anions on HOR/HER activities
- TEM images of supported metal electrocatalysts
- Procedure for calculating pH for buffer solutions and comparison between calculated and experimental values
- HOR/HER polarization curves on Vulcan XC-72 in electrolytes with different pH values
- Fig. S1. CVs of Pt/C, Ir/C, Pd/C, and Rh/C at different pH values.
- Fig. S2. CVs and HOR/HER polarization curves at different pH values on Pt/C.
- Fig. S3. CVs and HOR/HER polarization curves at different pH values on Ir/C.
- Fig. S4. CVs and HOR/HER polarization curves at different pH values on Pd/C.
- Fig. S5. CVs and HOR/HER polarization curves at different pH values on Rh/C.
- Fig. S6. CVs of Pt/C, Ir/C, Pd/C, and Rh/C in 0.1 M KOH.
- Fig. S7. Correlation of exchange current densities with Epeak.
- Fig. S8. Arrhenius plots of HOR/HER activities.
- Fig. S9. CO stripping profiles on Pt/C at different pH values.
- Fig. S10. CO stripping profiles on Ir/C at different pH values.
- Fig. S11. CO stripping profiles on Pd/C at different pH values.
- Fig. S12. CO stripping profiles on Rh/C at different pH values.
- Fig. S13. Effect of anions on HOR/HER activities.
- Fig. S14. TEM images and histograms of Pt, Ir, Pd, and Rh/C.
- Fig. S15. Comparison of calculated and electrochemically measured pH of the electrolytes.
- Fig. S16. HOR/HER polarization curves on Vulcan XC-72.
- Table S1. Particle size and surface area of Pt/C, Ir/C, Pd/C, and Rh/C.
- Table S2. Effect of anions on Hupd peak potentials and HOR/HER exchange current densities.
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