WO₃ Nanorods Bearing Interconnected Pt Nanoparticle Units as an Activity-Modulated and Corrosion-Resistant Carbon-Free System for Polymer Electrolyte Membrane Fuel Cells

Abstract

Commercial platinum-supported carbon (Pt/C) catalyst is the most widely used oxygen reduction reaction (ORR) electrocatalyst in polymer electrolyte membrane fuel cells (PEMFCs). However, carbon oxidation in Pt/C during the operation of PEMFCs poses serious issues, particularly in meeting long-term durability of the cells. Although carbon-free Pt-based catalysts are considered to be the best alternatives, the single-cell performances reported for many such systems are found to be inferior to that of the carbon-based systems. As a practical way to realize a carbon-free electrocatalyst, we have developed a system by dispersing an interconnected Pt nanoparticle network on the nanorods of tungsten oxide (WO3). Uniform dispersion of the WO3 nanorods by fine and more or less interconnected Pt nanoparticles (20 wt %) is a key feature of the electrocatalyst. This has helped the system to achieve an intrinsic ORR characteristics which is very similar to that of Pt/C, as reflected from the comparative analysis of the onset potential, half-wave potential, limiting current density, and the number of electrons transferred in the ORR process. Pt/WO3 also shows better stability under start–stop accelerated potential cycling after 10 000 cycles, compared to Pt/C. The relative decrement in the electrochemically active surface area (ECSA) for Pt/WO3 nanorods was negligible, compared to the ∼26% decrement registered by Pt/C under the identical testing conditions. Finally, a system-level validation in a single-cell model of PEMFC by fabricating a membrane electrode assembly (MEA) with Pt/WO3 as both the anode and cathode catalyst delivered comparable output power density as that of a similar system fabricated by using Pt/C. ECSA comparison in MEA shows the potential use of Pt/WO3-400 as the catalyst for the fuel cells, since it is exhibiting an ECSA value that is 3.4 greater than that of Pt/C at a Pt loading of 0.5 mg cm–2.

A comprehensive review of MXenes as catalyst supports for the oxygen reduction reaction in fuel cells

“…WO 3supported Pt has better electrocatalytic performance and stability than Pt/C. 102 Defected WO x has a bandgap between 2.6 and 2.8 eV and is considered an n-type semiconductor. 103 In addition, carbide-based tungsten or WCsupported catalysts were reported to have a large surface area (256 m 2 g À1 ) and are ideal for good metal catalyst dispersion.…”

Interfacial Engineering of Metal/Metal Oxide Heterojunctions toward Oxygen Reduction and Evolution Reactions

“…In comparison with carbon materials, metal oxides, especially reducible oxides, have more abundant electronic structures which make the catalytic activity and stability more tunable [36] . In fact, a large number of studies have shown that Pt particles supported on reducible oxides such as TiO 2 , [37] WO 3 , [38] SnO 2 , [39] NbO 2 , [40] and CeO 2 [41] exhibit good ORR activity in the past few years. Vogel et al.…”

“…WO 3 has relatively good electrical conductivity among metal oxides, especially when it has abundant oxygen vacancies or is hydride into hydrogen tungsten bronze (H x WO 3 ) [50] . Hence, WO 3 can be utilized as carbon‐free support for metals to prepare electrocatalysts [38,51] . Kurungot et al.…”

“…Kurungot et al. prepared Pt/WO 3 heterostructure and used it in fuel cells [38] . Pt/WO 3 shows similar intrinsic ORR characteristics to Pt/C while displaying better stability under start−stop accelerated potential cycling than Pt/C.…”

Metal–Support Interactions in a Molybdenum Oxide Anchored PtNi Alloy for Improving Oxygen Reduction Activity

“…Recently, some metal oxides (e.g., SnO 2 , TiO 2 , and WO x ) − with strong electrochemical stability have been developed as new supports for PEMFCs. Compared with carbon materials, metal oxides have high corrosion resistance, leading to improved catalyst stability.…”