Metal–Electrolyte Interfaces

Sulfate, Bisulfate, and Hydrogen Co-adsorption on Pt(111) and Au(111) in an Electrochemical Environment

“…On this account, the interaction of electrolytes with catalytic surfaces was studied intensively in the last decades (Groß, 2020 ; Nowicki and Wandelt, 2020 ). One of the best studied systems is sulfate adsorption on platinum (Shingaya and Ito, 1996 ; Kolics and Wieckowski, 2001 ; Herrero et al, 2002 ; Braunschweig et al, 2010 ; Garcia-Araez et al, 2010 ; Santana et al, 2010 ; Comas-Vives et al, 2013 ), but despite various investigations the surface structure of the ad-layer is still controversially discussed.…”

The electrostatic effect and its role in promoting electrocatalytic reactions by specifically adsorbed anions

“…1 The electrode surface is usually charged, and the ions of opposite sign enrich the electrolyte side of the EDL (Fig. 1) [2][3][4] Two general interactions within the EDL may significantly affect the energetics as well as the kinetics of electrocatalytic processes: (1) covalent interactions such as short-range chemical bonding between the electrocatalysts and the adsorbates (reactants, intermediates as well as spectators); (2) noncovalent interactions, including the electrostatic attraction or repulsion, hydrogen bonding, van der Waals interaction, etc. The structure of the EDL as well as the magnitude of such interactions can be altered by the control of the electrolyte composition (nature and concentrations of the cations/anions, solvent, and pH), the reaction conditions (applied potential, temperature and pressure), and so on.…”

“…[5][6][7][8][9][10] In previous studies, it was found that the specific adsorption of anions at an electrode/electrolyte interface usually displays a poisoning effect in most electrocatalytic processes. 2,9,[11][12][13][14] Typical examples are frequently encountered for reactions on Pt group electrodes, which are the best and benchmark catalysts for most electrocatalytic reactions. The existence of specifically adsorbed anions such as halide, sulfate, and phosphate in an electrolyte usually results in slower kinetics for both the oxidation of small organic molecules (SOMs) and the oxygen reduction reaction (ORR).…”

“…[13][14][15][16][17][18] The poisoning effect is attributed primarily to the blocking effect, e.g., occupying the active sites and inhibiting the adsorption of the reactants or intermediates. 2,9,11 As a result, all these anions are usually regarded as poisoning species. In contrast, a few studies have reported that the specific adsorption of anions could accelerate the kinetics of electrocatalytic reactions, including the hydrogen evolution reaction (HER), [19][20][21][22][23][24][25] ORR, 26,27 reduction reaction of CO 2 (CO 2 RR), [28][29][30] formic acid oxidation reaction (FAOR), [31][32][33][34] etc.…”

“…According to the right-hand side of eqn (2), Df M S consists of the contribution from six terms: (1) w M , the surface potential of the metal caused by the electron spillover from the metal electrode to the solution side, which may extend over several angstroms depending on the surface charge on the metal electrode and species in the electrolyte solution side which are in direct contact with the electrode. The value of w M is determined primarily by the total density of valence electrons of the electrode materials, which is in the range of several volts to more than ten volts (i.e., the largest potential drop in eqn (2). 51 Electronic interactions between electrode electrons and solution species in direct contact with the metal electrode may redistribute the electron spillover and consequently changes the value of w M .…”