Pt Sub-Monolayer on Au: System Stability and Insights into Platinum Electrochemical Dissolution

Abstract

Platinum is the best single element oxygen reduction reaction electrocatalyst. In recent years, several advanced catalysts have been suggested. One of them is the so-called “platinum monolayer electrocatalyst”. In this work we demonstrate the potential- and time-resolved dissolution characteristics of such sub-monolayer platinum supported on gold in potentiodynamic and potentiostatic regimes. It is shown that the as-prepared Pt@Au is not stable, but rather shows significant dissolution of both Pt and Au similar to the pure elements. Potential-resolved dissolution profiles reveal that anodic dissolution scales with Pt coverage, while cathodic dissolution and quasi-steady-state dissolution are Pt coverage independent. This implies a significantly higher Pt coverage normalized dissolution of Pt@Au, viz. a factor of four higher dissolution amounts for Pt coverage of 0.25. The onsets of Pt and Au dissolution are also comparable to the pure elements. Only after intermixing during potential cycling does the system become somewhat stabilized. The onset of Pt transient anodic dissolution shifts to more positive values. The data obtained in the current work provide new insights into the mechanism of platinum dissolution. It also aids the understanding of the previously observed effect of stabilization of Pt catalysts by addition of Au, and will therefore guide future developments for improving catalyst performance.

Addressing stability challenges of using bimetallic electrocatalysts: the case of gold–palladium nanoalloys

“…Similarly, Cherevko et al showed that the onset of Pt dissolution after intermixing shift to slightly higher potential than those of the pure elements. 73 Furthermore, in line with the oxide reduction peak shift (Fig. 1), the cathodic Pd dissolution of the alloyed material ends significantly earlier, one more time confirming a correlation between Pd-oxide reduction and cathodic dissolution processes.…”

“…72 Recently, however, Cherevko et al showed that a Pt sub-monolayer on bulk Au is not stable, but rather shows significant dissolution of both Au and Pt similar to the pure polycrystalline elements. 73 In our case, the Au and Pd dissolved masses in the alloy normalized by the nanoparticle total surface area (insets in Fig. 2A and B) are in absolute terms approximately half of those for the pure metals (for Pd ≈ 60%, for Au ≈ 50%).…”

Electrochemical On‐line ICP‐MS in Electrocatalysis Research

“…Representative is the utilization of SFC‐ICP‐MS with gradient composition libraries ( e. g. Pt 1−x Cu x for ORR and Ir 1−x Ru x for OER) for which high‐throughput activity and stability screening can be achieved. On‐line ICP‐MS is also indispensable when it comes to multielemental analysis, allowing simultaneous quantification of, e. g. Pt and Cu or Ir and Ru from the gradient libraries presented above, or Pt and Au from sub‐monolayer Pt covered Au, etc. Traditional techniques like rotating ring disk electrode (RRDE) or electrochemical quartz crystal microbalance (EQCM) fail in this.…”

Recent Advances in the Growth of Metals, Alloys, and Multilayers by Surface Limited Redox Replacement (SLRR) Based Approaches

“…Overall, the best choice of both ion concentrations would keep the fraction of electrodeposited growing metal lower than 1% during UPD layer formation [59]. The one-cell approach is very attractive with its operational simplicity and when applicable has been used by many groups for the purposes of fundamental or applied research involving SLRR deposition [60][61][62]. It ensures best efficiency in comparison with the shuttling and flow-cell methods as neither changes of electrolytes/water nor exposure to the environment ever take place in the one-cell deposition configuration.…”