We synthesized clean unsupported Pt nanoparticles (NPs) which can be used for any electrochemical measurements without the need for additional cleaning steps. In this report, we demonstrated the use of these unsupported Pt NPs for electrochemical reactions involving hydrogen. We further identified conditions under which Pt NPs deactivate in unpurified, reagent grade acid, and alkaline electrolytes, and differentiated between degradation mechanisms involving catalyst poisoning and particle growth. We monitored the degradation of Pt NPs as a function of a decrease in the electrochemically active surface area (ECSA) at different applied potentials. The results obtained from the ECSA measurements were then correlated with the identical location transmission electron microscopy (IL-TEM) observations. At potentials less than 1 V vs RHE, catalyst poisoning was found to be a dominant cause for degradation while particle growth was dominant at 1.5 V vs RHE in both acid and alkaline electrolytes.
Platinum is ubiquitous in electrochemical catalysis owing to its ability to accelerate redox reactions involving surface-bound hydrogen and oxygen. Accordingly, Pt is often used as a calibration standard and activity benchmark against which novel electrocatalysts are compared.These measurements are often executed in unpurified, reagent grade electrolytes where Pt is also susceptible to deactivation by several routes. This constitutes a challenge where the ease with which Pt-based electrocatalysis measurements can be executed must be balanced against the difficulty of making those measurements accurate and consistent. We report herein a synthetic procedure for catalytically active Pt nanoparticles that uses readily available reagents and laboratory apparatus, with the goal of making high-quality control experiments in electrocatalysis as easy as possible. We also identified conditions under which these particles deactivate in unpurified aqueous acid and base and differentiated between mechanisms involving catalyst poisoning, which dominates at more negative applied potentials, and particle growth, which dominates at positive potentials where Pt-oxide species are produced. Finally, we demonstrated that unsupported Pt nanoparticle films can be used to good effect for reference electrode cali-1 bration and benchmarking of hydrogen evolution/oxidation electrocatalysts, even in unpurified electrolytes, provided steps are taken to minimize the impact of deactivation.
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