Surface spectators and their role in relationships between activity and selectivity of the oxygen reduction reaction in acid environments

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Ciapina, Eduardo G. [UNESP]
Lopes, Pietro P.
Subbaraman, Ram
Ticianelli, Edson A.
Stamenkovic, Vojislav
Strmcnik, Dusan
Markovic, Nenad M.
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Abstract We use the rotating ring disk (RRDE) method to study activity-selectivity relationships for the oxygen reduction reaction (ORR) on Pt(111) modified by various surface coverages of adsorbed CN<inf>ad</inf> (Θ<inf>CNad</inf>). The results demonstrate that small variations in Θ<inf>CNad</inf> have dramatic effect on the ORR activity and peroxide production, resulting in volcano-like dependence with an optimal surface coverage of Θ<inf>CNad</inf> = 0.3 ML. These relationships can be simply explained by balancing electronic and ensemble effects of co-adsorbed CN<inf>ad</inf> and adsorbed spectator species from the supporting electrolytes, without the need for intermediate adsorption energy arguments. Although this study has focused on the Pt(111)-CN<inf>ad</inf>/H<inf>2</inf>SO<inf>4</inf> interface, the results and insight gained here are invaluable for controlling another dimension in the properties of electrochemical interfaces.
Catalyst selectivity, Electrocatalysis, Electrochemical interfaces, Electronic effects, Ensemble effects, Oxygen reduction reaction
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Electrochemistry Communications, v. 60, p. 30-33.