In Situ Stability Studies of Platinum Nanoparticles Supported on Ruthenium−Titanium Mixed Oxide (RTO) for Fuel Cell Cathodes

Abstract

Using a variety of in situ techniques, we tracked the structural stability and concomitantly the electrocatalytic oxygen reduction reaction (ORR) of platinum nanoparticles on ruthenium–titanium mixed oxide (RTO) supports during electrochemical accelerated stress tests, mimicking fuel cell operating conditions. High-energy X-ray diffraction (HE-XRD) offered insights in the evolution of the morphology and structure of RTO-supported Pt nanoparticles during potential cycling. The changes of the atomic composition were tracked in situ using scanning flow cell measurements coupled to inductively coupled plasma mass spectrometry (SFC-ICP-MS). We excluded Pt agglomeration, particle growth, dissolution, or detachment as cause for the observed losses in catalytic ORR activity. Instead, we argue that Pt surface poisoning is the most likely cause of the observed catalytic rate decrease. Data suggest that the gradual growth of a thin oxide layer on the Pt nanoparticles due to strong metal–support interaction (SMSI) is the most plausible reason for the suppressed catalytic activity. We discuss the implications of the identified catalyst degradation pathway, which appear to be specific for oxide supports. Our conclusions offer previously unaddressed aspects related to oxide-supported metal particle electrocatalysts frequently deployed in fuel cells, electrolyzers, or metal–air batteries.

Anisotropy of Pt nanoparticles on carbon- and oxide-support and their structural response to electrochemical oxidation probed by in situ techniques

“…Most importantly, Pt on RTO shows the lowest Pt dissolution representing an improved total electrochemical stability of an RTO-supported Pt electrocatalyst which we have previously shown. 62…”

“…This suggests RTO to be an interesting and promising support material for further investigations. 62 However, the degradation and dissolution of fuel cell catalysts is highly complex, and firm conclusions would be enhanced by perfectly defined materials with identical particle size, shape, loading and interparticle distance which are all known to impact Pt dissolution. [56][57][58][59] Furthermore, continued technique development that improves resolution could deconvolute closely spaced dissolution peaks.…”

Fabrication and Applications of 3D Nanoarchitectures for Advanced Electrocatalysts and Sensors

“…Several studies have demonstrated that the stability of electrocatalysts can be improved because of the decelerated dissolution of active materials and the prevention of their deformation, i.e., agglomeration. [167,168] Such dissolution or deformation, exemplified in Figure 2j,k, occur more spontaneously with smaller nanoparticles. In contrast, the larger volume materials or interconnected networks are more robust against those degradations.…”

Electrocatalysis for the Oxygen Evolution Reaction in Acidic Media: Progress and Challenges

“…A growing body of evidence shows that Rubased OER catalysts dissolve extensively during the electrocatalytic process [32]. This is because the onset potential of Ru-based catalysts is consistent with the corrosion potential of the metal Ru [48]. Ir-based catalysts also suffer similar degradation issues [49].…”