Effect of Loading, Alloying, and Support Material on Iridium Catalytic Activity Toward Ethanol Electro-oxidation in an Acidic Medium
Abstract
Fossil fuels contribute massively to environmental pollution and climate change. Therefore, fuel cells are a promising alternative source for clean, green, renewable, and sustainable energy. A fuel cell is a galvanic cell that directly transforms the chemical energy stored in a chemical fuel into electrical power. The proton-exchange membrane fuel cell is a standard fuel cell, while the direct ethanol fuel cell is nonstandard. In a direct ethanol fuel cell in an acidic media, ethanol fuel directly supplies the proton exchange membrane system. H+ generated at the anode pass through the proton exchange membrane to combine with O2 in air and the e- at the cathode to reduce O2 to H2O. Catalyst nanoparticles, Ir-based and Ir-alloyed, especially with Ru, are ideal electrocatalysts to speed up the electrochemical reaction in the DEFC. Besides, a catalyst support material allows the catalyst nanoparticles to disperse effectively on its surface. Carbon black and antimony-doped tin oxide, or ATO, are promising catalyst support materials in electrochemical reactions. In this study, Ir-based electrocatalysts with different loadings on ATO support were synthesized and characterized qualitatively and quantitively. Results show that the electrocatalyst with the highest Ir loading on ATO has the highest catalytic activity toward ethanol electro-oxidation in the acidic medium. Additionally, an Ir/C and an Ir-Ru alloyed electrocatalyst on carbon were synthesized and characterized to investigate the effect of alloying on the catalytic activity for the electrocatalysts. Results show that the Ir-Ru alloyed electrocatalyst on carbon support has higher catalytic activity toward ethanol electro-oxidation. Further, an Ir-Ru alloyed electrocatalyst on ATO was synthesized and characterized to compare the effect of the support material of this electrocatalyst with its counterpart on a carbon support. Results show that the ATO support for the alloyed electrocatalyst caused a sluggish IrOx formation/reduction. Lastly, the effect of support material for Ir-based electrocatalysts was investigated. Results show that Ir nanoparticles have better dispersion on the ATO