Influence of Anion Chaotropicity on the SO₂ Oxidation Reaction: When Spectator Species Determine the Reaction Pathway

Abstract

The electrochemical SO 2 oxidation reaction (SO 2 OR) is a promising alternative to the O 2 evolution reaction for H 2 electrochemical generation. The SO 2 OR exhibits a low thermodynamic potential and small kinetic barrier, and Au has been observed to be a very active catalyst. For this material, nonlinear dynamic behavior is observed, which is related to the electrolyte chaotropicity at the solid-liquid interface. In this work, the influence of the chaotropicity was investigated by electro-chemical and spectroelectrochemical techniques, and the main reasons for the dependence on the chaotropicity were investigated. The electrochemical response as a function of the chaotropicity was determined as a function of the mechanism observed, and the reaction pathway selection was related to the intermediate adsorption, which in turn was controlled by the interfacial water structure. The "neutral" chaotropicity was found to be the optimum condition for SO 2 OR.[a] Dr.

Gold–Rhodium Nanoflowers for the Plasmon-Enhanced Hydrogen Evolution Reaction under Visible Light

“…These bands correspond to water in the solvation shell of the potassium ions in the electrolyte (Figure S11). 76,82,91 Au and Au 68 Rh 32 showed a similar behavior, with small variations for this band (Figure 6e), indicating that the adsorption of solvated K + ions is weaker for these catalysts. Nonetheless, Rh NPs showed the highest slope in the Stark plots and wavenumber plots (Figure 6e,f), indicating that the interaction of rhodium with the solvated complex is much stronger in pure Rh NPs.…”

“…Since water should now be considered, it is also important to highlight that the water adsorption conformation affects the way the O–H bond will be more or less easily broken during the Volmer step . The electrochemical activity dependence on the water adsorption conformation is not new; actually, it was already proposed by Trasatti for the HER, and it has been shown in the literature that it can affect the electrochemical activity for different reactions. − Therefore, it is proposed that the water structure orientation at the double-layer region will give insights into investigations on the HER mechanisms …”

Effect of Adsorbed Sulfate on the Product Selectivity of Ethanol Oxidation on Pt Nanoparticles in Acidic Solution

“…Additionally, they modulate the adsorption energy, stabilize the reactants and intermediates, , adjust the spatial structure, , and change the potential distribution of adsorbates on the surface via local electrostatic interactions and H-bonds, which is beneficial for electrochemical reaction kinetics. The most obvious effect of adsorbed anions is their real participation in reaction pathway selection, , which can modify the reaction selectivity and sensitivity to external conditions …”

“…The adsorbed sulfate on the electrode is believed to inhibit reactions as a spectator species by competing with reactants for active sites on the surface . Meanwhile, it plays an important role in selecting the reaction pathway during oxidation reactions. ,,,, For example, the adsorbed sulfate shows a preference for the pathway of aldehyde and acid formation by reducing the number of available ensemble sites required for the CO 2 formation pathway, , resulting in higher local oxidation current . In turn, the strongly adsorbed products, such as acid, hinder oxidation in the form of adsorbed acetate. , Moreover, the adsorbed sulfate attracts reactants in solution and supports the active intermediate configuration by H-bonding and local electrostatic interactions, which facilitate the reaction.…”

“…14 Additionally, they modulate the adsorption energy, 15 stabilize the reactants 16 and intermediates, 10,17 adjust the spatial structure, 18,19 and change the potential distribution 20 of adsorbates on the surface via local electrostatic interactions and H-bonds, which is beneficial for electrochemical reaction kinetics. The most obvious effect of adsorbed anions is their real participation in reaction pathway selection, 21,22 which can modify the reaction selectivity and sensitivity to external conditions. 23 Understanding how electrolyte composition controls electrocatalytic reactions requires insight into electrode/electrolyte interaction; therefore, the speciation of the interfacial anion is of specific interest to many investigators.…”