The Crucial Role of Water in the Stability and Electrocatalytic Activity of Pt Electrodes

Abstract

Understanding the role of water in the activity and stability of electrocatalysts is of great interest for different fundamental reactions. Investigations aiming to expand understanding of this are very challenging in aqueous electrolytes. By contrast, nonaqueous electrolytes with very well-defined water content can provide ideal conditions to better clarify the role of water in electrochemical reactions. In this paper, the dissolution and electrochemical behavior of Pt during potentiodynamic and potentiostatic measurements in methanol-and acetonitrile-based electrolytes with accurately controlled water content of <1 ppm, 100 ppm, 1000 ppm, 1%, and 10% are studied. In methanol-based electrolytes, we demonstrate the promoting effect of small amounts of water on the methanol oxidation reaction. We show the formation of surface oxide species with increasing water content in the Pt dissolution profile, which develops from a purely anodic to a predominantly cathodic dissolution, a known characteristic of aqueous electrolytes. The effect of water on the electrode stability is fundamentally different in acetonitrile-based systems: presumably, the strong adsorption of solvent molecules competes with the adsorption of water and thus inhibits the formation of an oxide layer at the surface even up to a water concentration of 1% as revealed by potentiodynamic measurements.

Effect of Water Contamination on the Transition Metal Dissolution in Water-Enriched Electrolyte: A Mechanistic Insight into a New Type of Dissolution

“…“Cathodic” dissolution, therefore, seems to arise independently of prior structural damage because of TM dissolution when using LiPF 6 -based electrolytes. The emergence of reductive dissolution patterns in water-enriched nonaqueous electrolytes is well known for Pt substrates, as was demonstrated in a previous work by Ranninger et al They suppose that water enables the formation of surface Pt–O during anodic sweeping, which then desorbs on the subsequent cathodic sweep. However, in this case the “anodic”…”

On‐line Electrode Dissolution Monitoring during Organic Electrosynthesis: Direct Evidence of Electrode Dissolution during Kolbe Electrolysis

“…However, the expected increased cathodic Pt dissolution associated with the reduction of Pt−O can be observed. The onset of the oxide reduction, which is expressed as cathodic dissolution in the analysis, is shifted around 600 mV to negative potentials compared to pure methanol [9c] . We speculate that the substituted oxide layer, as described by Conway and Vijh, [16] is the reason for this shift.…”

“…The onset of the oxide reduction, which is expressed as cathodic dissolution in the analysis, is shifted around 600 mV to negative potentials compared to pure methanol. [9c] We speculate that the substituted oxide layer, as described by Conway and Vijh, [16] is the reason for this shift. The strongly adsorbed CH 3 COO species stabilize the underlying oxide.…”

“…First, Pt dissolution was measured in methanol containing LiOH or NEt 3 during Kolbe electrolysis of acetic acid. In the course of neutralization of acetic acid with LiOH, one equivalent of water is released, which can significantly influence the reaction as well as the electrode dissolution behavior [9c,10] . Compared to this water‐containing system, the system with NEt 3 base is practically water‐free.…”

“…In the course of neutralization of acetic acid with LiOH, one equivalent of water is released, which can significantly influence the reaction as well as the electrode dissolution behavior. [ 9c , 10 ] Compared to this water‐containing system, the system with NEt 3 base is practically water‐free. Hence, an additional electrolyte system with 1 mol L −1 acetic acid, 0.1 mol L −1 NEt 3 containing 0.1 mol L −1 H 2 O was also tested to pay heed to the effect of water.…”