In Situ AFM Imaging of Platinum Electrode Surface during Oxidation–Reduction Cycles in Alkaline Electrolyte

Abstract

The development of energy conversion systems depends strongly on our fundamental understanding of the electrochemical interface of the electrocatalyst. Here, we study the changes in the surface morphology of a platinum polycrystalline electrode during oxidation–reduction cycles in a wide potential window (0.05–2.0 V) in sodium hydroxide by in situ atomic force microscopy. Platinum nanoparticles are observed on the surface after cycling due to the redeposition of dissolved platinum ions. The influence of scan rate on platinum redeposition is studied by applying asymmetric potential sweep programs. The negative-going scan rate is the key factor here, as it controls the reduction of platinum oxide, as well as the redeposition of platinum. Moreover, it is found that chloride ions in the electrolyte impede the redeposition by complexing with platinum. This investigation enables us to reveal the surface roughening processes on platinum electrode in alkaline electrolyte and assists in understanding the fundamentals of the stability of platinum-containing energy conversion systems.

Potential‐Dependent Morphology of Copper Catalysts During CO2 Electroreduction Revealed by In Situ Atomic Force Microscopy

“…[22] However,while it has been used to follow structural changes of Cu electrodes under applied potential, [22e] STM was carried out mostly in basic and acidic electrolytes and in potential regimes below the onset of CO 2 RR due to experimental limitations. [22b,d] Electrochemical atomic force microscopy (EC-AFM) has been applied to am uch lesser extent to study growth and dissolution processes on (electro)catalyst surfaces [23] and at copperelectrolyte interfaces in particular. [24] So far, neither EC-AFM nor EC-STM have been reported on copper electrodes during CO 2 RR in relevant electrolytes and at highly gasevolving potential regimes.…”

Base-Accelerated Degradation of Nanosized Platinum Electrocatalysts

“…With Pt dissolution seeming similar in both the acid and the base, it appears that Pt redeposition differs between acidic and alkaline Pt/C degradation. 24,25,28 This hypothesis relies on alkaline electrolytes containing hydroxide ions, which form complexes with dissolved Pt. As a result, the dissolved Pt is stabilized in base and is more likely to diffuse prior to redeposition.…”

“…26 This difference is underscored by recent work indicating that acidbased literature does not necessarily translate to Pt in a base: at high pH levels, bulk Pt experiences more transient dissolution than at that at low pH levels. 24,25,27,28 Additionally, carbonsupported platinum (Pt/C) nanoparticles suffer increased Ptcatalyzed corrosion of the carbon support in base. 29,30 Understanding these degradation processes in base is essential because Pt/C particles are used in large-scale anion-exchange fuel cells that operate under alkaline conditions.…”

Thin Film Electrodes for Anodic Stripping Voltammetry: A Mini-Review

“…Such work may also lead to MTFEs with improved ASV performance in neutral and alkaline electrolytes, opening doors to new applications for the technique. New fields of study could include electrochemical fuel cells, where electrocatalytically active metals like Pt are known to dissolve and redeposit in the alkaline electrolytes (Deng et al, 2019). As in the Zn assays performed by our group to evaluate alkaline battery separators (Duay et al, 2017a;Duay et al, 2018;Kolesnichenko et al, 2020;Arnot et al, 2021), Sn or Bi MTFEs may be useful in quickly and simply quantifying this dissolution.…”