Electro-Oxidation of CO Saturated in 0.1 M HClO4 on Basal and Stepped Pt Single-Crystal Electrodes at Room Temperature Accompanied by Surface Reconstruction
Abstract
:1. Introduction
2. Materials and Methods
3. Results and Discussion
3.1. CVs on Pt Single-Crystal Surfaces in CO-Saturated HClO4
3.2. Potential Stepping on Pt(111) in CO-Saturated HClO4
- At 0.95 V, the surface was continuously deactivated by the simultaneous formation of surface oxides (Figure 5, Equations (1) and (2)). Pt adatoms or Pt clusters with low CNs were preferentially oxidized. Those oxidized species were immobile on the surface.
- The current density at 0.60 V, after being treated at 0.95 V, became much smaller (Figure 5) along with the formation of a stable CO adlayer on the terraces (Figure 6). Pt(CO)42+ (Equation (4)) or Pt(CO)2 (Equation (5)) species were also formed after the potential step by the reduction of the (single or several atomic) Pt oxides. We believe that, at least partially, Pt(CO)42+ remained on the surface at 0.60 V after the potential step from 0.95 V, because Pt oxides were not completely reduced to metal Pt at 0.60 V after going through 0.95 V, as seen in the CVs obtained in pure HClO4 (Figure 2, Figure 3 and Figure 4). Because the reactivity did not change very much at 0.60 V, the surface morphology did not change either. Therefore, the planar and electronically charged Pt(CO)42+ species, inactive towards the bulk CO electro-oxidation, might be immobile on the Pt surface.
- At 0.05 V, all Pt(CO)42+ species became Pt(CO)2. The current density at 0.60 V after treatment at 0.05 V became larger than that after treatment at 0.95 V (Figure 5), because of the formation of Pt(0)(CO)2 from Pt(II)(CO)42+; metallic Pt species can be active towards bulk CO electro-oxidation. The reaction rate, on the other hand, was continuously lowered at 0.60 V. This is because of the deposition of mobile Pt(CO)2 at the energetically favorable adjacent site on the surface, thus lowering its CN and eventually its reaction activity.
- Repeating the treatments at 0.05 and 0.95 V gradually decreased the reaction rate of the bulk CO electro-oxidation in the lower potential region (Figure 5). The potential cycling between 0.07 and 0.95 V much enhanced the deactivation process on Pt electrodes (Figure 2, Figure 3 and Figure 4) compared with the potential-step treatment (Figure 5), possibly because of the continuous morphological change during the potential cycling.
4. Conclusions
Supplementary Materials
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Pt(111)-Oriented | Pt(110)-Oriented | Pt(100)-Oriented | |||||
---|---|---|---|---|---|---|---|
Pt(111) | Pt(10 9 8) | Pt(432) | Pt(110) | Pt(431) | Pt(100) | Pt(10 2 1) | |
Onset potential/V vs. RHE | 0.37 | 0.43 | 0.42 | 0.35 | 0.40 | 0.29 | 0.35 |
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Abe, K.; Uchida, H.; Inukai, J. Electro-Oxidation of CO Saturated in 0.1 M HClO4 on Basal and Stepped Pt Single-Crystal Electrodes at Room Temperature Accompanied by Surface Reconstruction. Surfaces 2019, 2, 315-325. https://doi.org/10.3390/surfaces2020023
Abe K, Uchida H, Inukai J. Electro-Oxidation of CO Saturated in 0.1 M HClO4 on Basal and Stepped Pt Single-Crystal Electrodes at Room Temperature Accompanied by Surface Reconstruction. Surfaces. 2019; 2(2):315-325. https://doi.org/10.3390/surfaces2020023
Chicago/Turabian StyleAbe, Kiyotaka, Hiroyuki Uchida, and Junji Inukai. 2019. "Electro-Oxidation of CO Saturated in 0.1 M HClO4 on Basal and Stepped Pt Single-Crystal Electrodes at Room Temperature Accompanied by Surface Reconstruction" Surfaces 2, no. 2: 315-325. https://doi.org/10.3390/surfaces2020023
APA StyleAbe, K., Uchida, H., & Inukai, J. (2019). Electro-Oxidation of CO Saturated in 0.1 M HClO4 on Basal and Stepped Pt Single-Crystal Electrodes at Room Temperature Accompanied by Surface Reconstruction. Surfaces, 2(2), 315-325. https://doi.org/10.3390/surfaces2020023