Iridium–Ruthenium Alloyed Nanoparticles for the Ethanol Oxidation Fuel Cell Reactions

Abstract

In this study, carbon supported Ir−Ru nanoparticles with average sizes ranging from 2.9 to 3.7 nm were prepared using a polyol method. The combined characterization techniques, that is, scanning transmission electron microscopy equipped with electron energy loss spectroscopy, high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction, were used to determine an Ir−Ru alloy nanostructure. Both cyclic voltammetry and chronoamperometry (CA) results demonstrate that Ir 77 Ru 23 /C bears superior catalytic activities for the ethanol oxidation reaction compared to Ir/C and commercial Pt/C catalysts. In particular, the Ir 77 Ru 23 /C catalyst shows more than 21 times higher mass current density than that of Pt/C after 2 h reaction at a potential of 0.2 V vs Ag/AgCl in CA measurement. Density functional theory simulations also demonstrate the superiority of Ir−Ru alloys compared to Ir for the ethanol oxidation reaction. D irect ethanol fuel cells (DEFCs) have attracted much attention as a renewable energy source for both portable and stationary electronic applications because of several unique characteristics of ethanol fuel such as availability from biomass production, low toxicity, and safety for storage and transportation in liquid form. 1−3 Although ethanol may be considered a promising and productive fuel for fuel cell reactions, research and development of DEFC technology has been hindered by the lack of cost-effective anode catalysts. Platinum (Pt)-based nanostructured materials have commonly been used as excellent anode catalysts for electro-oxidation of small organic molecules (SOMs) because of the high catalytic activity of Pt for dissociation of SOMs. Ethanol oxidation reaction (EOR) is a complex twelve-electron transfer reaction, which involves various reaction intermediates such as acetaldehyde, acetic acid, carbon monoxide, and other dehydrogenation fragments. 4,5 These strongly adsorbed reaction intermediates, CO in particular, can block active sites on the surface Pt and exacerbate the charge transfer considerably. Also, the high expense of Pt metal has seriously restricted their implementation for commercial application.Several notable theoretical and experimental efforts have gone into developing active effective catalysts with high activity and selectivity toward the EOR. 6−15 Mavrikakis, Nørskov, and co-workers recently reported that several Platinum Group Metals (PGMs) including Pt, Pd, Ir, Rh, and Ru could decompose ethanol effectively using both experimental and theoretical methods. 16 Among these five PGMs, catalysts containing Pt, Pd, Rh, and Ru have been well demonstrated for the EOR. However, Ir-based electrocatalysts have only been reported in limited studies for the oxygen reduction reaction and oxidation of SOMs. 8,17−21 Recently, experimental and theoretical efforts from our group found the highly active Ir−Sn heterogeneous nanocatalysts for the EOR, strongly demonstrating the potential of Ir metal as an alternative catalyst in fuel cell rea...

Ethanol and Water Adsorption on Transition-Metal 13-Atom Clusters: A Density Functional Theory Investigation within van der Waals Corrections

“…1,2 Most of ethanol SRR catalysts are based on transition-metal (TM) particles supported on oxide compounds, namely, TM particles of Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au supported on oxides such as MgO, La 2 O 3 , ZnO, CeO 2 , Al 2 O 3 , ZrO 2 , V 2 O 5 , SnO 2 , and SiO 2 have been studied for ethanol SRR. [1][2][3][6][7][8][9][10][11][12][13][14] Among those TM/oxides systems, Co/ZnO, 14 Rh/Al 2 O 3 , Rh/CeO 2 , 15 and Ni/La 2 O 3 −Al 2 O 3 , 13 have yielded excellent performance, [1][2][3]8 however, it depends also on the catalysts preparation method, which can affect ethanol conversion and H 2 selectivity.…”

“…Although several experimental studies have been reported for ethanol SRR on TM NPs supported on oxides, [1][2][3][6][7][8][9][10][11][12][13][14]23,24 there is a lack of theoretical studies to obtain an atomistic understanding of the interaction of ethanol and water with TM particles with few atoms. For example, most of the experimental 25,26 and theoretical [26][27][28][29][30][31][32][33][34][35] studies have focused on the study of the interaction of water and ethanol with compact TM surfaces employing density functional theory 36,37 (DFT) and the slab geometry model.…”

Photoelectrochemical Oxidation of Ethanol under Visible Light Irradiation on TaON-Based Catalysts

“…Iridium and its oxides has been described as good co-catalyst, and when combined with Pt, PtRu and PtSn it increases the alcohols oxidation in acidic medium. [69][70][71][72] The addition of iridium and its oxides improves the catalytic activity and stability of these materials due to the preferential adsorption of hydroxyl groups on these species at lower potentials, favoring the oxidation of the ethanol intermediates adsorbed in the catalyst surface. inset of Fig.…”

Iridium Application in Low‐Temperature Acidic Fuel Cells: Pt‐Free Ir‐Based Catalysts or Second/Third Promoting Metal in Pt‐Based Catalysts?

“…Acetaldehyde was an intermediate product, but the major product of ethanol oxidation on Ir electrodes was acetic acid. The addition of a second element such as Sn [85,86] or Ru [87] remarkably increases the EOR activity of Ir. By CV measurements at room temperature, the peak current value on Ir/C was lower than that on Pt/C, in agreement with Fujiwara et al [83] However, the onset potential of ethanol electro-oxidation on Ir/C was much lower than on Pt/C.…”