Electrochemical stability and degradation of commercial Rh/C catalyst in acidic media.

• Electrochemical stability of Rh/C was studied by accelerated degradation protocols. • IL-SEM and ex-situ TEM were used to study local nanoscale degradation mechanisms. • EFC-ICP-MS was used to track Rh dissolution during degradation tests. • Severe degradation of Rh/C occurs during cycling between 0.05 V RHE and 1.4 V RHE. • Degradation of Rh/C occurs via dissolution followed by re-deposition. Electrochemical stability of a commercial Rh/C catalyst has been studied in an acidic electrolyte by accelerated degradation protocols (ADP) which involved 5000 rapid voltammetric scans (1 V/s) in two potential regions: ADP1 was performed between 0.4 V RHE and 1.4 V RHE , while ADP2 was performed between 0.05 V RHE and 1.4 V RHE. Degradation of Rh/C was monitored by the changes in Rh electrochemical surface area (ECSA) and electrocatalytic activity for hydrogen evolution (HER) and oxygen reduction (ORR). Rh/C catalyst was particularly stable during ADP1 showing only a minor loss of ECSA, while its electrocatalytic activity for HER and ORR was practically unaffected, which was further corroborated with identical location SEM (IL-SEM) imaging. In the case of ADP2, severe degradation of Rh/C occurred followed by substantial decay in its electrocatalytic activity. Coupling of the electrochemical flow cell (EFC) with ICP-MS revealed much higher Rh dissolution in ADP2 than in ADP1. IL-SEM in combination with ex-situ TEM imaging showed that degradation of the Rh/C sample is not homogeneous during ADP2, as dissolution prevails on certain locations, while dissolution followed by re-deposition occurs on others. According to the results obtained in this work, Rh/C catalysts are exceptionally sensitive to the sudden potential jumps between particularly low and high values. [Display omitted] [ABSTRACT FROM AUTHOR]