A Study on Workability and Durability of Different Plating Thickness of Silver on Monel As a Cathode Material for Oxygen Reduction

Abstract

Listen

Translate article

The higher overvoltage for the oxygen reduction reaction (ORR) limits the performance of electrochemical system such as alkaline fuel cell, deoxygenation cell, etc. where the higher oxygen reduction rate is desirable. Silver, having similar mechanism for oxygen reduction as platinum, is one of the cheaper alternative as oxygen reduction. Silver plated on suitable substrate can significantly decrease the cost of oxygen reduction material. The study focuses on the cathodic property of four different silver plating thickness (0.2, 0.5, 1.0, 2.0 µm) on monel, high nickel-copper alloy, for oxygen reduction, and their durability in oxygen reduction process. A special two chamber electrochemical cell separated by cation exchange membrane (CEM), is constructed for conducting the electrochemical experiments. The experiments were performed at room temperatures and 0.5 M NaCl solution and seawater was used as electrolyte. The potentiodynamic and potentiostatic test were performed for the analysis of oxygen reduction property of different thickness of silver on monel. The anodic polarization and scanning electron microscope (SEM) were used for studying the durability of the specimen, with focus on erosion and erosion induced corrosion of the silver plated monel. The electrochemical experiments were performed with the dimensionally stable anode (DSA) and the saturated calomel electrode (SCE) as counter electrodes. The current density for oxygen reduction for four different thickness silver layer was similar, and the oxygen reduction to water by 4- electron pathways was evident in on all samples. The plated layer of 0.2 µm was observed to be the most affected sample and there was observation of small pits throughout the surface. There was no significant effect on 0.5, 1.0 and 2.0 µm silver plated layer. Energy-dispersive x-ray spectroscopy (EDS) showed the formation calcium hydroxide on the surface of the cathode material after 48 hours potentiostatic test on seawater. The result indicate that the durability is of more concern than electrochemical property for oxygen reduction on different thickness silver plated layer on monel.