Structurally Ordered Low‐Pt Intermetallic Electrocatalysts toward Durably High Oxygen Reduction Reaction Activity

Abstract

Carbon-supported low-Pt ordered intermetallic nanoparticulate catalysts (PtM 3 , M = Fe, Co, and Ni) are explored in order to enhance the oxygen reduction reaction (ORR) activity while achieving a high stability compared to previously reported Pt-richer ordered intermetallics (Pt 3 M and PtM) and low-Pt disordered alloy catalysts. Upon high-temperature thermal annealing, ordered PtCo 3 intermetallic nanoparticles are successfully prepared with minimum particle sintering. In contrast, the PtFe 3 catalyst, despite the formation of ordered structure, suffers from obvious particle sintering and detrimental metal-support interaction, while the PtNi 3 catalyst shows no structural ordering transition at all but significant particle sintering. The ordered PtCo 3 catalyst exhibits durably thin Pt shells with a uniform thickness below 0.6 nm (corresponding to 2-3 Pt atomic layers) and a high Co content inside the nanoparticles after 10 000 potential cycling, leading to a durably compressive Pt surface and thereby both high activity (fivefold vs a commercial Pt catalyst and 1.7-fold vs an ordered PtCo intermetallic catalyst) and high durability (5 mV loss in half-wave potential and 9% drop in mass activity). These results provide a new strategy toward highly active and durable ORR electrocatalysts by rational development of low-Pt ordered intermetallics.

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

“…In the literature, intermetallic alloys have already caught much attention due to their promising ORR performance ( Gamler et al., 2018 ; Hodnik et al., 2014 ; Li and Sun, 2019 ; Pavlišič et al., 2016 ; Rößner and Armbrüster, 2019 ; Zhang et al., 2020 ). However, although we can find many reports on intermetallic alloys of Pt-Cu ( Bele et al., 2014 ; Gatalo et al, 2019a , 2019b , 2019c , 2019d ; Hodnik et al., 2012a , 2014 ; Pavlišič et al., 2016 ) and Pt-Fe ( Liu et al., 2019 ; Wang et al., 2019b ; Wittig et al., 2017 ), the reports on intermetallic phases of more industrially relevant Pt-Co ( Cui et al., 2020 ; Xiong et al., 2019 ) and even more so Pt-Ni alloys ( Lu et al., 2009 ) are still very scarce ( Leonard et al., 2011 ; Zou et al., 2015 ). Careful examination of the XRD spectra also reveals the presence of pure M phases in Pt-M/C electrocatalysts containing Fe, Ni, and Co ( Figure 3 D; as pointed by the arrows).…”

“…Pt-Fe alloy seems like a good choice for similar reasons as Pt-Cu. Formation of the intermetallic phases is rather facile and widely present in the literature ( Liu et al., 2019 ; Wang et al., 2019b ; Wittig et al., 2017 ). However, in terms of applicability of Pt-Fe alloy electrocatalysts in PEMFC, similarly, but perhaps even more significantly, as in the case of Cu, even slightest amounts of Fe ions in the PEMFC are not acceptable.…”

Oxygen Reduction Reaction Catalyzed by Carbon-Supported Platinum Few-Atom Clusters: Significant Enhancement by Doping of Atomic Cobalt

“…Yet, despite substantial progress in the alkaline media, it remains challenging to achieve a viable activity in acid, as compared to Pt/C. The other is to reduce the amount of Pt used and hence to diminish the catalyst cost but without compromising the electrocatalytic performance [ 10 – 14 ]. One intuitive strategy is to reduce the size of Pt NPs by taking advantage of the increasing surface-to-volume ratio and hence enhanced utilization of the Pt atoms.…”

Achieving Superior Electrocatalytic Performance by Surface Copper Vacancy Defects during Electrochemical Etching Process

“…Carbon‐supported Pt‐based catalysts are the most widely applied electrocatalysts in fuel cells for both the cathodic reduction and the anodic oxidation reaction . However, poor durability, high cost, and insufficient reaction kinetics are the major shortages for their wide commercial applications .…”