Tracing Pd and Pt Release during the Hydrogen Evolution Reaction Using Inductively Coupled Plasma Mass Spectrometry: Metal Dissolution, Nanoparticle Detachment, or Catalyst Layer Instability?

Inductively coupled plasma mass spectrometry (ICP-MS) has become a crucial tool for the real-time analysis of electrochemical processes, such as (photo)corrosion, electrodeposition, and electrocatalytic reactions occurring at high electrode potentials. In this study, we provide insights into a previously unexplored phenomenon: the release of metal from thin-film electrodes composed of metal nanoparticles supported on high-surface-area carbon under hydrogen evolution reaction (HER) conditions. By combining ICP-MS with electrochemistry, we show that the extent of metal release is controlled by the HER activity of the metal: it is more pronounced for Pt than Pd, increases with lower potential limits, and is exacerbated by slower potential sweep rates. Identical-location transmission electron microscopy images reveal that the metal release arises from the detachment of a small fraction of the thin-film electrode and not from metal dissolution or nanoparticle detachment from the carbon support. We recommend strategies to mitigate this adverse effect, such as reducing the catalyst layer thickness and increasing the ionomer-to-carbon ratio. Our findings highlight the risk of misinterpreting catalyst layer detachment as metal dissolution in online ICP-MS studies and are of practical importance for water electrolyzers.