Simulation of interfacial pH changes during hydrogen evolution reaction

• The hydrogen evolution reaction was modeled by finite element method.
• The effect of different boundary conditions on the interfacial pH change was studied.
• Depending on conditions, changes in pH up to 4.2 pH units were observed.
• Even in the presence of a buffer solution, significant variations of pH were obtained.

This work investigates the possibility of interfacial pH changes during a hydrogen evolution reaction using a finite elements simulation approach. This reaction is a common side step observed in many electrochemical systems, such as electrodeposition or corrosion. To develop a general approach, different mechanisms, i.e., Volmer/Tafel and Volmer/Heyrovský, were investigated. It is observed that for V-H mechanism the interfacial pH change increases 4.2 pH units for those cases where the bulk pH is 5.0. Therefore, in this case, the instant pH at the interface become alkaline, although the bulk is still acidic, which could justify parallel reactions such as metal hydroxide formation in metal electrodeposition. Besides, the interfacial pH changes and the corresponding pH profiles were calculated under several experimental conditions including the composition of the metallic electrode, the bulk solution pH and the total buffer concentration ([HA] + [A−]).

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