Resolving the nanoparticles' structure-property relationships at the atomic level: a study of Pt-based electrocatalysts

Abstract

Summary Achieving highly active and stable oxygen reduction reaction performance at low platinum-group-metal loadings remains one of the grand challenges in the proton-exchange membrane fuel cells community. Currently, state-of-the-art electrocatalysts are high-surface-area-carbon-supported nanoalloys of platinum with different transition metals (Cu, Ni, Fe, and Co). Despite years of focused research, the established structure-property relationships are not able to explain and predict the electrochemical performance and behavior of the real nanoparticulate systems. In the first part of this work, we reveal the complexity of commercially available platinum-based electrocatalysts and their electrochemical behavior. In the second part, we introduce a bottom-up approach where atomically resolved properties, structural changes, and strain analysis are recorded as well as analyzed on an individual nanoparticle before and after electrochemical conditions (e.g. high current density). Our methodology offers a new level of understanding of structure-stability relationships of practically viable nanoparticulate systems.

Efficient catalytic combustion of toluene at low temperature by tailoring surficial Pt0 and interfacial Pt-Al(OH)x species

“…Of all the supports, γ-Al 2 O 3 was ranked as the most studied and used one for the catalytic combustion of VOCs, due to its large specific surface area, thermostability, and low cost ( Huang et al., 2015 ). Besides, the particle sizes of noble metals could also regulate the chemical state of noble metals and influence their performance ( Du et al., 2020 ; Moriau et al., 2021 ; Wang et al., 2020a ; Zhang et al., 2020b ). Several studies have proposed that the turnover frequencies (TOFs) would increase as the increase of particle size, due to the exposure of more Pt crystal facets, such as (100) and (111), which provided more active sites for the catalytic reaction ( Huang et al., 2014 ).…”

Influence of Electrochemical Pretreatment Conditions of PtCu/C Alloy Electrocatalyst on Its Activity

“…It is well known that platinum doping with some d-metals increases the catalyst activity due to a number of effects, as follows: (1) a change in the electronic structure of the metal; (2) a decrease in the interatomic distance in the metal crystal lattice, which contributes to the dissociative adsorption of oxygen molecules; (3) a change in the surface oxides' composition and an increase in the corrosion resistance of the alloy in comparison to pure Pt [4][5][6]. One of the important points that is limiting the use of bimetallic catalysts is the leaching of the alloying component, which results in the poisoning of the proton-exchange membrane and the degradation of the membrane electrode assembly (MEA) [7,8]. Therefore, one of the current research areas of the present paper is the catalyst's synthesis with nanoparticles of the following structures: core-shell [4,[9][10][11], gradients [12,13], hollow [14][15][16], porous frameworks [17,18], nanowires, and nanodendrites [19][20][21].…”

Understanding the Crucial Significance of the Temperature and Potential Window on the Stability of Carbon Supported Pt-alloy Nanoparticles as Oxygen Reduction Reaction Electrocatalysts

“…In the case of Pt-alloy NPs, one also has to deal with the dissolution of the less noble metal dissolution. 25,26 Last but not least, closely connected to the dissolution of Pt and Ostwald ripening, general understanding of Pt redeposition phenomena in the catalyst layer is also of utmost importance. [27][28][29] However, perhaps equally important as improving the intrinsic durability of an electrocatalyst is also understanding how the mentioned degradation mechanisms relate to the different operating conditions in a PEMFC.…”

“…SFC-ICP-MS along with other recently used similar methodologies 25,26,29,[38][39][40][41][42] enables insights into the time-and-potential resolved dissolution of metals, providing yet another dimension to the observed electrochemical signal. Specifically to the above-mentioned work by Cherevko and co-workers 37 , the authors reported a rather significant influence of temperature on the onsets of both the Pt-oxide formation as well as the reduction.…”

“…In the case of Pt-alloys, cathodic and anodic dissolution of Pt is then always followed by also dissolution of the less noble metal. 25,26 The rate of this process is then defined by the UVL/UPLthe lower we go, the more Pt-oxide we reduce, subsequently triggering a higher degree of metal dissolution. While this might not be of a particular importance for pure-Pt cathodes, aging of the Pt-alloy cathode will not only result in the decrease in kinetic performance, but also additional degradation phenomenon related with the presence of the less noble metal ions in the catalyst layer and/or the membrane.…”