General Strategy for Synthesis of Ordered Pt₃M Intermetallics with Ultrasmall Particle Size

Abstract

Controllable synthesis of atomically ordered intermetallic nanoparticles (NPs) is crucial to obtain superior electrocatalytic performance for fuel cell reactions,b ut still remains arduous.Herein, we demonstrate anovel and general hydrogel-freezed rying strategy for the synthesis of reduced graphene oxide (rGO) supported Pt 3 M( M= Mn, Cr,F e, Co, etc.) intermetallic NPs (Pt 3 M/rGO-HF) with ultrasmall particle size( about 3nm) and dramatic monodispersity.T he formation of hydrogel prevents the aggregation of graphene oxide and significantly promotes their excellent dispersion, while af reeze-drying can retain the hydrogel derived threedimensionally (3D) porous structure and immobilize the metal precursors with defined atomic ratio on GO support during solvent sublimation, which is not afforded by traditional oven drying. The subsequent annealing process produces rGO supported ultrasmall ordered Pt 3 Mi ntermetallic NPs ( % 3nm) due to confinement effect of 3D porous structure. Such Pt 3 Mi ntermetallic NPs exhibit the smallest particle size among the reported ordered Pt-based intermetallic catalysts.A detailed study of the synthesis of ordered intermetallic Pt 3 Mn/ rGO catalyst is provided as an example of ag enerally applicable method. This study provides an economical and scalable route for the controlled synthesis of Pt-based intermetallic catalysts,w hichc an pave aw ay for the commercialization of fuel cell technologies.The need for the practical application of fuel cells has motivated the search of new electrocatalysts with enhanced activity and durability beyond the traditionally employed carbon-supported Pt and Pt-M alloys (M = transition metal). Intermetallic phases,featuring atomically ordered structures, have attracted increasing research attention over the last decade because of their exceptional electronic and structural properties. [1] In contrast to disordered Pt À Ma lloys (solid solution), ordered PtÀMintermetallic compounds have welldefined stoichiometries and provide much better control of the local geometry of metal atoms,r esulting in uniform distribution of active sites on the same surface plane.M ore importantly,t he stronger lattice strain of Pt on intermetallic surfaces can provoke as hift of the d-band center and the change of electronic structure of the surface Pt. This change in electronic structure endows PtÀMintermetallic catalysts with better activity and structural/chemical stability.T od ate, numerous studies have been conducted to investigate PtÀM intermetallic electrocatalysts (M = Fe, [2]

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

“…Furthermore, although the producer has not revealed their exact thermal annealing protocol, we anticipate that the observed crystal structures of the alloy nanoparticles would anyway differ even at the same thermal treatments due to unique phase diagrams of analyzed Pt-M combinations. 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 ).…”

“…Rö ßner and Armbrü ster, 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, 2019aGatalo et al, , 2019bGatalo et al, , 2019cGatalo et al, , 2019dHodnik et al, 2012aHodnik et al, , 2014Pavli si c 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).…”

Highly dispersed L10-PtZn intermetallic catalyst for efficient oxygen reduction

“…S12). This good morphology stability toward migration and agglomeration is beneficial for maintaining high ORR performance [34,35]. With regard to composition changes, since the second metals are usually difficult to preserve due to their more active chemical properties, we investigated the electrolyte composition changes of Pt and Zn at different cycles during ADTs.…”

Synthesis of noble metal-based intermetallic electrocatalysts by space-confined pyrolysis: Recent progress and future perspective

“…In general, the available active sites of disordered alloys are usually limited in the certain regions due to the random site occupancy. On the contrary, the well-defined structure in intermetallics could ensure the uniform distribution of active sites [57,58]. Additionally, the lower free energy of formation and stronger chemical bonding, including metallic and covalent/ionic bonding, provide the intermetallic materials with higher structural and chemical stability than the disordered counterparts.…”