Electrolyte Effects on Single Crystal Cyclic Voltammograms

Insights into the governing mechanisms relevant for electrocatalytic energy conversion is of fundamental interest for future energy schemes aimed at combating fossil dependence and anthropogenic CO₂ emissions.¹ Electrocatalytic reactions occur at an electrode's surface-electrolyte interface (see figure 1a). In this interface both geometric and electronic effects determine the selectivity and efficiency of the electrocatalytic reaction.^2,3 Simultaneously, the structure and properties of the electrochemical interface are affected not only by the potential applied to the electrocatalyst, but also the pH of the solute⁴ as well as the cations/anions present in the electrolyte.^3,5

Given recent advances on the generalized computational hydrogen electrode (GCHE)⁶ it is now possible to predict the most probable surface structure using ab initio molecular dynamics (AIMD) and density functional theory (DFT). These structures can be represented as 2D phase diagrams of the interface at any given potential. Herein, we present the basic methodology for creating such diagrams and how to correlate these with experimental cyclic voltammograms (CVs).⁷ CVs of Pt(111) under different electrolyte conditions (see figure 1b) have been investigated using a rotating disk electrode (RDE) setup and compared with DFT calculations. Our work addresses the impact cations, anions and pH have on the surface of Pt(111) electrodes and what one may extrapolate when contemplating real fuel cell devices.

We herein show that combining experimental model studies with theoretical calculations through the GCHE framework opens up for a new and powerful tool for interpreting CVs of well-ordered metallic M(hkl) interfaces⁸ for a wide range of electrocatalytic reactions.

References

1. S. Chu, and A. Majumdar, Nature, 488, 294–303 (2012);

2. K. D. Jensen, J. Tymoczko, J. Rossmeisl, A. S. Bandarenka, I. Chorkendorff, M. Escudero-Escribano, and I. E. L. Stephens, Angew. Chemie Int. Ed., 57, 2800–2805 (2018);

3. D. Strmcnik, M. Escudero-Escribano, K. Kodama, V. R. Stamenkovic, A. Cuesta, and N. M. Marković, Nat. Chem., 2, 880–885 (2010);

4. A. Bagger, L. Arnarson, M. H. Hansen, E. Spohr, and J. Rossmeisl, JACS, 141, 1506–1514 (2019);

5. R. Rizo, E. Herrero, and J. M. Feliu, PCCP, 15, 15416 (2013);

6. J. Rossmeisl, K. Chan, R. Ahmed, V. Tripkovic, and M. E. Björketun, PCCP, 15, 10321 (2013);

7. J. Rossmeisl, K. D. Jensen, A. S. Petersen, L. Arnarson, A. Bagger, and M. Escudero-Escribano, Submitted-under review, (2020);

8. A. Bagger, R. M. Arán‐Ais, J. H. Stenlid, E. Campos dos Santos, L. Arnarson, K. D. Jensen, M. Escudero‐Escribano, B. R. Cuanya, and J. Rossmeisl, ChemPhysChem, 20, 3096-3105 (2019);

Figure 1