Toward in Situ Dissolution Monitoring of Platinum Nanoparticles by Optimized Online Inductively Coupled Plasma Mass Spectrometry Measurement

Platinum (Pt) nanoparticles (NPs) are an indispensable catalyst in polymer electrolyte fuel cells (PEFCs), but their durability remains a critical challenge. This study systematically evaluated the effect of the gasket thickness (d_g) in the measurement cell on the detection responsivity of online inductively coupled plasma mass spectrometry (ICP-MS) measurement using constant-current anodic pulse dissolution tests of Cu and potential cycling tests of Pt. While a smaller d_g enhanced the detection responsivity, no significant improvement was observed for d_g ≤ 100 μm. A deconvolution process was successfully used to reconstruct the original dissolution signals, enabling in situ evaluation of the dissolution behavior of bulk Pt and Pt NPs, even with broadened detection profiles. The effect of d_g on the electrochemical measurements, including the solution resistance (R_sol) and cyclic voltammogram (CV), was also investigated. Larger d_g reduced R_sol and mitigated the influence of side reactions. The latter allowed accurate CV shapes to be obtained, enabling reliable analysis of the dissolution behavior of Pt. A Pt/C catalyst (Pt NPs) was evaluated under potential cycling conditions using the optimized online ICP-MS conditions. The dissolution behavior of the Pt/C catalyst was consistent with that of bulk Pt, but the Pt/C catalyst dissolved at significantly lower potentials than bulk Pt owing to the Gibbs–Thomson effect. These results highlight the importance of optimizing the experimental conditions for accurately assessing the dissolution behavior of NPs. This study provides a foundation for designing high-durability catalysts to extend the longevity and enhance the performance of PEFCs by enabling precise in situ monitoring of the dissolution mechanism.