W₂C-Supported PtAuSn—A Catalyst with the Earliest Ethanol Oxidation Onset Potential and the Highest Ethanol Conversion Efficiency to CO₂ Known till Date

Abstract

The electrocatalytic behavior of a tungsten carbide-supported Pt(3 wt %)Au(3 wt %)Sn(10 wt %) catalyst (PtAuSn/W 2 C) is investigated toward the oxidation of ethanol at temperatures below 70 °C. Vulcan XC-72-supported Pt(3 wt %)Au(3 wt %)Sn(10 wt %) is used as a reference (PtAuSn/C). For a better understanding of the reaction mechanism, in situ techniques such as electrochemical mass spectrometry (EC-MS) and Fourier transform infrared spectroscopy (FTIRS) are employed. We show that PtAuSn/W 2 C has a higher electrocatalytic performance than PtAuSn/C, with a CO 2 conversion efficiency of 6.5% detected at 0.65 V versus the reversible hydrogen electrode (RHE) at room temperature with on-line quantitative EC-MS measurements. FTIR spectra analysis and EC-MS during the ethanol oxidation reaction (EOR) show C−C bond breaking at the admission potential (0.05 V RHE ) and an onset potential for the CO 2 formation at E ≥ 0.20 V RHE . The CO tolerance of Pt nanoparticles in PtAuSn/W 2 C is improved by the presence of oxide species on W 2 C through a bifunctional mechanism, as well as the electronic charge transfer from the W 2 C support to the metallic nanoparticles through an electronic effect.

Advanced Catalytic Materials for Ethanol Oxidation in Direct Ethanol Fuel Cells

“…In addition to the widely-developed nanowires, many novel nanostructures, such as nanocages and nanoframes, have been constructed to accommodate more abundant active sites and large surface-area-to-volume ratios. Also, a few ternary metal-based catalysts (such as PtCuNi [68], PtRhNi [61], PtMoNi [69], and PtAuSn [70]) with precise composition control have shown increased EOR selectivity. The PtRhNi polyhedra nanoparticles [71] were chemically etched to form Pt-skin PtRhNi nanoframes which were then attached with SnO 2 nanoparticles [61] (Figure 4f-i).…”

“…Recent studies have been extended to develop diverse alternatives to replace the carbon black, such as carbon nanotubes, graphene, metal oxides, metal hydroxides, and their hybrids. Moreover, a few self-supported promoters have also been developed, such as Fe 2 P [59], W 2 C [70], and MoS 2 [76]. Further, flexible and conductivity substrates can also serve as promising supports for Pt-and Pd-based catalysts.…”

“…Transition metal carbides, especially W 2 C and Mo 2 C, possess superior electrical conductivity and ultrahigh chemical and thermal stabilities and have been considered as promising support materials in electrocatalytic fields [70,100,101]. Ternary PtAuSn catalysts supported on W 2 C present much higher catalytic activities towards EOR in acid solution and at increasing temperatures of up to 70 • C when compared to PtAuSn/C catalysts [70]. This mainly benefits from the W 2 C-induced bifunctional mechanism and the additional charge transfer from W 2 C support to alloy catalysts.…”

“…The implementation of both composition and microstructure control plays important roles in promoting the electrocatalytic activity and durability of various candidates for EOR. Furthermore, in combination with the optimization, many hybrid catalysts have been developed for promising applications in DEFCs [70]. Despite the significant progress achieved, the anode catalysts for ethanol electro-oxidation still suffer from low efficiency and durability in converting ethanol to CO 2 , thereby leaving much room for further improvement to accommodate the commercial application of DEFCs.…”

“…Considering the intricate byproducts produced in EOR, it is critical to utilize in-situ test and observation tools to reveal the dynamic reaction processes, including in-situ Fourier transform infrared spectroscopy (FTIRS), on-line differential electrochemical mass spectrometry (DEMS) and in-situ Raman spectroscopy [70,75].…”