Supporting Information Effects of Loading and Nafion Content on the Activity and Stability of Iridium Oxygen Evolution Reaction Catalysts Matej Zlatara,b,*, Cornelius Simonb, Joanna M. Przybysza, b, Miquel Gamón Rodríguezc, Jakob Katsmanb, Marc Ayouba, b, Ivan Khalakhanc, Serhiy Cherevkoa,* aForschungszentrum Jülich GmbH, Helmholtz-Institute Erlangen-Nürnberg for Renewable Energy (IET-2), Cauerstrasse 1, 91058 Erlangen, Germany bDepartment of Chemical and Biological Engineering, Friedrich-Alexander-Universität ErlangenNürnberg, Egerlandstr. 3, 91058 Erlangen, Germany cDepartment of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 18 000 Praha 8, Czech Republic *Corresponding authors: E-mail address:
[email protected];
[email protected]
Figure S1. Tafel plots of metallic Ir as a function of loading, derived from LSVs shown in Figure 1a and measured by SFC. Figure S2. a) Total anodic charge (ECSA) of metallic Ir, integrated from Figure 1a over the 0.4 – 1.4 VRHE range and normalized by the total Ir mass in the sample. b) Applied current density during galvanostatic hold, normalized by Ir mass (left) and ECSA (right). All measurements were done by the SFC.
Figure S3. Applied current density during galvanostatic hold of metallic Ir, normalized by Ir mass (left) and ECSA (right), plotted against Ir dissolution normalized by surface area a) and by Ir mass b). c) Potential measured and d) Overpotential at the end of the galvanostatic hold as a function of Ir loading. All measurements were done by the SFC. Figure S4. Influence of Ir loading on OER activity and electrochemistry of metallic Ir. a), b) and c) CVs (0.4 – 1.4 VRHE, 50 mV s-1, 4 cycles). d), e) and f) LSVs (1.2 – 1.55 VRHE, 10 mV s-1). a), b) are
normalized by surface area, c), d) by Ir mass, and e), f) by total anodic charge. All data were measured using RDE at 1600 RPM. Figure S5. a) Total anodic charge (ECSA) of metallic Ir, integrated from Figure S4a over the 0.4–1.4 VRHE range and normalized by the total Ir mass in the sample. b) Potential measured and c) Overpotential at the end of the galvanostatic hold as a function of Ir loading. d) Integrated dissolution profiles during a 5 mA cm-2 hold. e) Percentage activity loss, normalized by surface area (left) and ECSA (middle), percentage ECSA loss (right). Activity and ECSA loss were estimated from LSVs (at 1.6 VRHE) and CVs, respectively, before and after the 5 mA cm-2 hold. All data were measured using RDE at 1600 RPM. Figure S6. Influence of drop-casting procedure on metallic Ir OER activity. a) CVs (0.4 – 1.4 VRHE, 50 mV s-1, 4 cycles). b) LSVs (1.2 – 1.6 VRHE, 10 mV s-1). All measurements are done using RDE at 1600 RPM.
Figure S7. a) Ir ECSA integrated from Figure 2a over the 0.4–1.4 VRHE range and normalized by the total metallic Ir mass in the sample. b) Potentials measured during applied 5 mA cm-2 hold. c) Applied current density during galvanostatic hold, normalized by Ir ECSA for various Nafion contents. All measurements were done by the SFC. Figure S8. Applied current density during galvanostatic hold of metallic Ir normalized by ECSA, plotted against Ir dissolution normalized by surface area, measured using the SFC.
Figure S9. Influence of Nafion content on OER activity and electrochemistry of metallic Ir as measured by RDE. a), b) and c) CVs (0.4 – 1.4 VRHE, 50 mV s-1, 4 cycles). d), e) and f) LSVs (1.2 – 1.6 VRHE, 10 mV s-1). a), b) are normalized by surface area, c), d) by Ir mass, and e), f) by total anodic charge.
Figure S10. a) Total anodic charge (ECSA) of metallic Ir, integrated from Figure S9a over the 0.4–1.4 VRHE range and normalized by the total Ir mass in the sample. b) Potential measured and c) Integrated dissolution profiles during a 5 mA cm-2 hold. d) Percentage activity loss, normalized by surface area (left) and ECSA (middle), percentage ECSA loss (right). Activity and ECSA loss were estimated from LSVs (at 1.6 VRHE) and CVs, respectively, before and after the 5 mA cm-2 hold. All data were measured using RDE. Figure S11. Effect of Nafion application method on metallic Ir in RDE: mixed into ink vs. postdeposition drop-cast.
Figure S12. a) ECSA of IrO2 integrated from Figure 3a over the 0.4–1.4 VRHE range and normalized by the total Ir mass in the sample. b) Potential measured during galvanostatic hold of IrOx and b) Applied current density normalized by Ir ECSA, plotted against Ir dissolution normalized by surface area a) and by Ir mass. All measurements were done by the SFC. Figure S13. SEM images of IrO2 at the low and high magnifications as a function of Nafion content.
Figure S14. SEM images of metallic Ir at the low and high magnifications as a function of Nafion content. Figure S15. SEM images showing the coffee-ring effect in IrO2 (top) and metallic Ir (bottom) as a function of Nafion content. Original images were processed in ImageJ using a yellow inverted lookup table and contrast enhancement to improve ring visibility.
