Role of ZSM-5/AC hybrid support on the catalytic activity of Pd-Ag electrocatalysts towards ethanol oxidation: An experimental and kinetic study

Abstract

Ethanol is a promising future fuel for Direct Alcohol Fuel Cells (DAFCs) and one of the significant half-cell reactions of this type of FC is ethanol oxidation reaction (EOR). However, the high cost, low selectivity of the catalyst towards complete oxidation of ethanol to CO2, and poor electrode kinetics are the key challenges in commercializing this technology. The way to mitigate these issues is to design affordable, stable, and highly efficient electrocatalysts. In this prospect, we developed a zeolite-carbon (ZSM-5/AC) supported Pd-Ag binary alloy catalysts via a simple co-impregnation followed by co-reduction method. The influence of ZSM-5/AC composite support and its composition on the activity of bimetallic Pd-Ag catalyst has been studied in detail. The PdAg/ZSM-5/AC electrocatalyst with 1:3 wt ratio of ZSM-5:AC exhibited better catalytic performance (10.9 mA cm−2) and tolerance towards intermediate species than PdAg/AC and Pd/AC electrocatalysts. The larger jf/jb (forward to backward current density ratio) of 2.8 for PdAg/ZSM-5/AC indicates lower carbonaceous species accumulation on the zeolite-modified electrode. Additionally, the material possessed a good long-term cyclic stability up to 500 cycles. The high activity observed for PdAg/ZSM-5/AC could be attributed to synergism between bimetallic catalysts and high surface area zeolite support. Overall, the study reveals that the Pd-Ag bimetallic and ZSM-5/AC are potentially efficient electrocatalyst and support, respectively, for the ethanol oxidation reaction in DEFC application.