Base-Accelerated Degradation of Nanosized Platinum Electrocatalysts

Abstract

In the pursuit of a hydrogen economy, extensive research has been directed at developing acidic and alkaline hydrogen fuel cells. Such fuel cells often utilize platinum-based catalysts. These materials have been studied extensively in acidic conditions but not in alkaline ones. This focus on acidic systems creates a marked knowledge gap, since recent studies indicate that carbon-supported platinum (Pt/C) electrocatalysts degrade more rapidly in bases than in acids. Addressing this gap, the present work investigates Pt/C degradation at pH 2 and pH 12 using electrochemistry, transmission electron microscopy (TEM), and in situ X-ray absorption spectroscopy (XAS). TEM and XAS reveal accelerated Pt/C degradation at high pH levels, which results in increased Ostwald ripening, Smoluchowski agglomeration, and nanoparticle detachment. These processes are driven by platinum-catalyzed carbon corrosion and the dissolution and redeposition of platinum nanoparticles. Although these processes take place at both low and high pH levels, basic conditions accelerate the degradation. Base-enhanced Pt dissolution and redeposition was assessed in further detail, revealing an oxidation onset reduction of 100 mV in the base; however, there were no significant differences between undissolved Pt oxidation in acid and in base. The results suggest that soluble Pt oxidation products are stabilized in the base instead. These conclusions are important for translating acidbased literature to alkaline conditions.

Carbon Shell on Active Nanocatalyst for Stable Electrocatalysis

“…More specifically, active sites on catalyst materials are easily changed by dissolution, detachment, phase transitions, and deposition during electrochemical device operation, resulting in the loss of catalytic activity . To investigate these issues, significant effort has been expended to better understand the degradation mechanisms of nanostructured electrocatalysts under reaction conditions. − In addition, several synthetic approaches have been proposed to obtain durable catalyst structures and maintain the initial activity over time. − Nevertheless, there can be a trade-off between obtaining an active structure and a durable structure, limiting the optimization of a single catalyst structure. As a result, the use of additional structural units in catalyst design will be useful for enhancing the overall stability while maintaining optimal catalyst activity.…”

Materials for electrocatalysts in proton exchange membrane fuel cell: A brief review

“…Several studies have been conducted to investigate the degradation mechanism of Pt/C in PEMFC (Weber et al, 2018;Labata et al, 2021;Fan et al, 2022). The studies were aimed at understanding the degradation mechanism of Pt-based electrocatalyst to help researchers in developing mitigation strategies that could significantly reduce the cost of PEMFC (Lopes et al, 2020;Hersbach et al, 2021). Different perspectives exist in the literature on the cause of Ptbased electrocatalyst disintegration.…”

Electrolyzed–Reduced Water: Review II: Safety Concerns and Effectiveness as a Source of Hydrogen Water

“…However, since metal electrodes are still used, one cannot rule out the possibility of metal contamination in the drinking water. Nevertheless, this risk may also be mitigated by the neutral-pH machines because (i) neutral pH is not as corrosive on the electrodes, whereas basic conditions accelerate degradation of platinum electrodes [ 72 ], (ii) a lower current density results in less electromigration and mechanical stress and less electrode degradation [ 73 ], (iii) neutral-pH devices produce lower heat on the electrodes, which also decreases the debonding of the platinum [ 73 ], and (iv) some certain metal impurities are more prone to leaching and/or more soluble and thus more bioavailable at higher pHs (e.g., platinum, lead, chromium, arsenic, aluminum, etc.) [ 74 , 75 ].…”