Journal
APPLIED CATALYSIS A-GENERAL
Volume 483, Issue -, Pages 85-96Publisher
ELSEVIER
DOI: 10.1016/j.apcata.2014.06.029
Keywords
Iridium; Alloys; Fuel cell; Ethanol oxidation; Density functional theory
Categories
Funding
- National Science Foundation [CBET-1159662, 1159662]
- Div Of Chem, Bioeng, Env, & Transp Sys
- Directorate For Engineering [1159662] Funding Source: National Science Foundation
Ask authors/readers for more resources
Current ethanol oxidation catalysts in direct ethanol fuel cells (typically platinum-based) suffer from low conversion and are susceptible to CO poisoning. We therefore determined to find viable alternative catalysts for ethanol oxidation based on iridium using density functional theory to model bimetallic alloy (1 1 1) surfaces. Iridium was alloyed with another transition metal (from groups 4 through 11), M, in an overlayer (one layer of metal M on top of bulk iridium) or subsurface configuration (M inserted under the first layer of iridium). Segregation energies were calculated and the subsurface configuration was found to be most stable configuration in the majority of alloy cases under vacuum conditions. Select alloys (including Ir-Pt and Ir-Rh) showed a reversal of preferred alloy state (overlayer or underlayer) upon adsorption of CO. CO adsorption was modeled and lower CO adsorption energies were found for many alloys compared to pure Pt, indicating less CO poisoning. Complete oxidation of ethanol is typically limited by the breaking of strong C-C bonds, so any catalyst must lower the barriers for C-C bond breaking. Activation energies for C-C bond breaking (by considering a representative intermediate molecule CHCO) were lowered for the vast majority of the alloys used in an underlayer structure, reinforcing the significance of the underlayer structures or subsurface alloys. Finally, we found, based on CO adsorption energy, activation energy for C-C breakage reaction, and metal cost, three important catalyst descriptors, a number of promising catalysts for the ethanol oxidation reaction, such as alloys with M = Zr, Nb, Mo, W, Ru, Os, or Re. Experimental verification (cyclic voltammetry and chronoamperometry for ethanol oxidation) on Ir, Ir-Ru, and Ir-Rh catalysts confirmed the superiority of these Ir-based catalysts compared to Pt. Our results demonstrate that alloys of Ir show promise as more affordable substitutes for platinum group metals. (C) 2014 Elsevier B.V. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available