Effects of heat treatment atmosphere on the structure and activity of Pt₃Sn nanoparticle electrocatalysts: a characterisation case study

Abstract

Comprehensive identification of the phases and atomic configurations of bimetallic nanoparticle catalysts are critical in understanding structure-property relationships in catalysis. However, control of the structure, whilst retaining the same composition, is challenging. Here, the same carbon supported Pt 3 Sn catalyst is annealed under air, Ar and H 2 resulting in variation of the extent of alloying of the two components. The atmosphere-induced extent of alloying is characterised using a variety of methods including TEM, XRD, XPS, XANES and EXAFS and is defined as the fraction of Sn present as Sn 0 (XPS and XANES) or the ratio of the calculated composition of the bimetallic particle to the nominal composition according to the stoichiometric ratio of the preparation (TEM, XRD and EXAFS). The values obtained depend on the structural method used, but the trend air < Ar < H 2 annealed samples is consistent. These results are then used to provide insights regarding the electrocatalytic activity of Pt 3 Sn catalysts for CO, methanol, ethanol and 1-butanol oxidation and the roles of alloyed Sn and SnO 2 .

Regioselective generation and reactivity control of subnanometric platinum clusters in zeolites for high-temperature catalysis

“…The formation of such subnanometric Pt-SnOx interfacial structure can explain the absence of Pt-Sn bonding in the EXAFS results, since Pt and Sn are not in the form of conventional PtSn alloy nanoparticles. [32][33][34][35]…”

Phase Segregated Pt–SnO2/C Nanohybrids for Highly Efficient Oxygen Reduction Electrocatalysis

“…As shown in Scheme S1, Supporting Information, by virtue of its low‐melting‐point (232 °C) and ease of oxidation, the Sn is easily separated from the PtSn NPs, and further transformed into SnO 2 by the simple but effective process of annealing (at 300 °C) in static air. [ 25 ] The annealing temperature affected the particle size and content of surficial/interfacial oxygen in PtSnO 2 /C, which could further affect their ORR activity. It was found that 300 °C was the optimum annealing temperature (see the Supporting Information for details).…”

Contrasting the EXAFS obtained under air and H2 environments to reveal details of the surface structure of Pt–Sn nanoparticles

“…However, the results must be interpreted with caution as the environment in which the XAS data were acquired can have a significant effect. The well-studied Pt-Sn nanoparticles (Pt as the host metal and Sn as the guest), catalysts for alkane dehydrogenation [23][24][25][26][27][28] and electrocatalysts for CO and alcohol oxidation, 4,8,[29][30][31] may be used as an example. Decreases in the Sn-Pt bond length of 0.03 to 0.15 Å have been reported compared to that of the Pt 3 Sn structure.…”