Design of PtSn Nanocatalysts for Fuel Cell Applications

Abstract

The challenges in the fuel cell industry lie in the cost, performance, and durability of the electrode components, especially the platinum-based catalysts. Alloying has been identified as an effective strategy to reduce the cost of the catalyst and increase its efficiency and durability. So far, most studies focused on the design of PtM bimetallic nanocatalyst, where M is a transition metal. The resulting PtM materials show higher catalytic activity, but their stability remained challenging. In addition, most of the transition metals M are expensive or low abundant. Tin (Sn) has gained attention as alloying element due to its versatility in manufacturing both anode and cathode electrodes. If used as anode catalyst, it is able to overcome poisoning from CO and related intermediates. As cathode catalyst, it improves the kinetics of the oxygen reduction reaction (ORR). Additionally, Sn is an abundant and cheap element. The current contribution outlines the state of the art on the alloy and shape effect on PtSn activity and stability, demonstrating its high potential to develop cheaper, more efficient and durable catalysts for fuel-cell electrodes. Additionally, in situ analytical and spectroscopic studies can shed light on the elementary steps involved in the use of PtSn catalytic systems. Finally, this intriguing material can be used as a parent system for the synthesis of high-entropy-alloys and intermetallics materials.

Keywords: Alloys; Intermetallics; Mobility; Nanoparticles; sustainability.

Figure 1

Schematic of the operating principles of PEMFCs. Reproduced from Ref.  with permission from the Royal Society of Chemistry.

Figure 2

Schematic of the Methanol Oxidation Reaction. Reproduced from Ref.  with permission from the Royal Society of Chemistry.

Figure 3

Summary of the ethanol oxidation reaction (EOR) mechanism on Pt. Path on the left is preferred onto Pt(111) and at high surface coverages and the path on the right side is dominant at low coverages on stepped surfaces and defects. Adsorbates pictured in black were found experimentally and molecules in blue are present in solution. Reprinted with permission from Melke, J.; Schoekel, A.; Dixon, D.; Cremers, C.; Ramaker D. E.; Roth, C. Ethanol Oxidation on Carbon‐Supported Pt, PtRu, and PtSn Catalysts Studied by Operando X‐ray Absorption Spectroscopy. J. Phys. Chem. C 2010, 114, 5914–5925. Copyright 2010 American Chemical Society.

Figure 4

Schematic of the LOHC‐DIFC system. Reproduced from Ref.  with permission from the Royal Society of Chemistry.

Scheme 1

Structural parameters determining the properties of bimetallic nanocrystals.

Figure 5

Segregation energies before and during ORR of various bimetallic PtM catalyst (M=Co, Ni, Cu, Rh, Pd, Ag, Ir, Au, and Sn). E_seg is the segregation energy of a clean surface (Equation 6), whereas E_seg‐OCS is the segregation energy upon adsorption of oxygen‐containing species (OCS) during ORR (Equation 7). Reproduced from Ref.  with permission from the Royal Society of Chemistry.

Figure 6

XRD pattern with TEM image inset of Pt : Sn at different molar ratios (a) 90 : 10 and (b) 80 : 20 Reprinted with permission from Wang, X.; Altmann, L.; Stoever, J.; Zielasek, V.; Bäumer, M.; Al‐Shamery, K.; Borchert, H.; Parisi, J.; Kolny‐Olesiak, J. Pt/Sn Intermetallic, Core/Shell and Alloy Nanoparticles: Colloidal Synthesis and Structural Control, Chemistry of Materials, 2013, 25, 1400–1407. Copyright 2013 American Chemical Society.

Figure 7

a) XRD patterns of different PtSn intermetallic systems; b) cell potential as a function of Sn content (at %); c) effect of the thermal treatment on Pt₃Sn/C catalysts in the cell performace of a DEFC. These figures were published in International Journal of Hydrogen Energy, 44, F. Colmati, M. Magalhães, R. Sousa, E. Ciapina and E. Gonzalez, Direct Ethanol Fuel Cells: The influence of structural and electronic effects on Pt−Sn/C electrocatalysts, 28812–28820, Copyright Elsevier (2019).

Figure 8

PtSn1 NP a) and c), PtSn9 NW (b) and (d) before and after ADT, respectively. Inset is the lattice parameter of Pt (0.227 nm); e) mass activity (MA) decay of various PtSn morphology. PtSn1 is the nanoparticle, PtSn5, PtSn7, and PtSn9 are the nanowires in increasing aspect ratio (L/D). Reproduced from Ref.  with permission from the Royal Society of Chemistry.

Figure 9

(a) Nyquist Plot of Pt₃Sn NF, Pt₃Sn NP and Pt/C and (b) zoomed‐in region for resistance measurement. Reprinted with permission from Zhu, Y.; Bu, L.; Shao, Q.; Huang, X. Structurally Ordered Pt₃Sn Nanofibers with Highlighted Antipoisoning Property as Efficient Ethanol Oxidation Electrocatalysts, ACS Catalysis, 2020, 10, 3455–3461. Copyright 2020 American Chemical Society.

Figure 10

CA result at 1.0 V after CO‐purging at 200s and reaction time of 5000s (a) Pt₃Sn NFs−L/C, (b) Pt₃Sn NPs/C, and (c) Pt/C in 0.1 M HClO₄+0.5 M CH₃CH₂OH solution. Reprinted with permission from Zhu, Y.; Bu, L.; Shao, Q.; Huang, X. Structurally Ordered Pt₃Sn Nanofibers with Highlighted Antipoisoning Property as Efficient Ethanol Oxidation Electrocatalysts, ACS Catalysis, 2020, 10, 3455–3461. Copyright 2020 American Chemical Society.

Figure 11

Simulation structure of sub‐1‐nm PtSn hexagonal‐ultrathin sheet. This figure was published in Journal of Colloid and Interface Science, 545, Jee‐Yee Chen, Suh‐Ciuan Lim, Chun‐Hong Kuo, Hsing‐Yu Tuan, Sub‐1 nm PtSn ultrathin sheet as an extraordinary electrocatalyst for methanol and ethanol oxidation reactions, 54–62, Copyright Elsevier (2019)

Scheme 2

Overview of the in situ/operando techniques for the advanced characterization of PtSn nanoparticles. a) Potential dependent Fourier Transform Infrared (FTIR) spectroscopy. This figure was published in International Journal of Hydrogen Energy, 37, T. Herranz, S. García, M. V. Martínez‐Huerta, M. A. Peña, J. Fierro, F. Somodi, I. Borbáth, K. Majrik, A. Tompos and S. Rojas, Electrooxidation of CO and methanol on well‐characterized carbon supported PtxSn electrodes. Effect of crystal structure, 7109–7118, Copyright Elsevier (2012). b) Mössbauer spectroscopy. Reprinted with permission from Alcala, R.; Shabaker, J. W.; Huber, G. W.; Sanchez‐Castillo M. A.; Dumesic, J. A. Experimental and DFT studies of the conversion of ethanol and acetic acid on PtSn‐based catalysts, J. Phys. Chem. B 2005, 109, 2074–2085. Copyright 2005 American Chemical Society. c) Solid State Nuclear Magnetic Resonance (SS NMR spectroscopy). Reproduced from Ref. with permission from the Royal Society of Chemistry. d) X‐ray Absorption Spectroscopy (XAS) and its modification. Reproduced under terms of the CC‐BY license. Copyright (2019), Maoyu Wang et al., published by Springer. e) Differential Electrochemical Mass Spectrometry (DEMS). Reproduced from Ref. with permission from the Royal Society of Chemistry. f) Electron Microscopy characterization. This figure was published in Chem, 5, T. Ma, S. Wang, M. Chen, R. V. Maligal‐Ganesh, L.‐L. Wang, D. D. Johnson, M. J. Kramer, W. Huang and L. Zhou, Toward Phase and Catalysis Control: Tracking the Formation of Intermetallic Nanoparticles at Atomic Scale, 1235–1247, Copyright Elsevier (2019).

Figure 12

a) Scheme of the catalytic activity changes of PtSn@mSiO₂ catalysts during the reaction process. b) TEM images and HAADF‐STEM elemental distribution of Pt and Sn in the PtSn@mSiO₂ iNPs after different treatments. The initial state (a, b and c), after decarbonization (d, e and f) and after regeneration (g, h and i). Scale bars: 20 nm in a, d and g; 10 nm in b, e and h; 5 nm in c, f and i. HAADF‐STEM: c, f and i; yellow spots: Pt, blue spots: Sn. Reproduced from Ref. with permission from the Royal Society of Chemistry.

Figure 13

Design of HEI catalyst based on PtSn intermetallics, where the Pt and Sn sites are partially substituted by Co/Ni and In/Ga, respectively, forming a PtSn‐type HEI (PtCoNi) (SnInGa). Reproduced under terms of the CC‐BY license. Copyright (2022), Feilong Xing et al., published by Springer Nature.