Quantitative Study of Non‐Covalent Interactions at the Electrode–Electrolyte Interface Using Cyanide‐Modified Pt(111) Electrodes

Super-Nernstian Shifts of Interfacial Proton-Coupled Electron Transfers: Origin and Effect of Noncovalent Interactions

“…For the sake of comparison a line with a slope of -0.059 V, corresponding to the Nernstian behaviour expected for a PCET has also been included (dashed line). 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Metal cations in the electrolyte can interact with the nitrogen atoms of CN ad , thus blocking the sites where the PCET occurs, 6,20 and increasing the concentration of alkali-metal cations above a cation-dependent threshold concentration provokes a negative shift of the onset of hydrogen adsorption on cyanide-modified Pt(111) electrodes. 6 However, in the experiments reported in Fig.…”

Atomic Ensemble Effects in Electrocatalysis: The Site‐Knockout Strategy

“…[32] We have recently suggested that the increase in DG 0 of H upd is due to the formation of (CN ad ) x -H clusters. [32,33] Formation of adsorbed isocyanide (CNH ads ) was also argued by Schardt et al [34] (who suggested that the whole surface of the cyanidemodified Pt(111) electrode behaves as a polyprotic acid) in order to explain the effect of pH on the amount of Cs + retained on the surface of a cyanide-modified Pt(111) electrode after immersion in a 0.1 mm CsCl solution. The formation of (CN ad ) x -H clusters (where x must decrease with decreasing potential within the H upd region) can also explain the change in the Stark tuning rate of the CN stretching frequency of a cyanide-modified Pt(111) electrode occurring at potentials more negative than 0.6 V versus RHE [26d, 27e] (coinciding with the onset of H upd formation) and the incomplete blocking of hydrogen adsorption after adsorption of CO to saturation on a cyanide-modified Pt(111) electrode.…”

“…[33] Another interesting observation in Figure 4 is that, contrary to H upd , hydrogen evolution seems not to be affected by the presence of cyanide on cyanide-modified Pt(111) electrodes. It has been shown that overpotential-deposited hydrogen (H opd , i.e., hydrogen adsorbed at potentials more negative than the equilibrium potential for the hydrogen evolution reaction), and not H upd , is the reaction intermediate in the hydrogen evolution reaction.…”

“…Furthermore, the most solid proof of the lack of electronic effects on cyanide-modified Pt(111) electrodes is provided by comparing the density of states (DOS), as calculated using DFT, of clean Pt(111) and cyanide-modified Pt(111) surfaces [33] ( Figure 5). As can be seen, the DOS of the Pt atoms directly bonded to the CN ads is shifted to lower energies, as expected for strong bonding, but the DOS of the atoms that are (111) surface, thus supporting the notion that the effect of CN ad on the electronic properties of the platinum atoms that remain free is negligible.…”

Influence of the alkali metal cations on the activity of Pt(111) towards model electrocatalytic reactions in acidic sulfuric media

“…While certain progress in explaining the effect of the electrolyte components on the activity has been achieved quantitatively [42], it is often difficult to predict all possible interactions between cations and anions at the electrode surface. However, it is possible to roughly reveal some of the possible interactions by using experimental voltammetric data.…”