A Versatile Electrodeposition Approach to Controlled Modification of Pd on Sb Towards Efficient Electrocatalysis for Application in Direct Methanol Fuel Cells

Abstract

A bimetallic Sb-Pd electrocatalyst was prepared through a versatile two-step electrodeposition method using chronopotentiometry, i.e., a controlled amount of Sb was electrodeposited onto glassy carbon (GC) electrode followed by electrodeposition of Pd to obtain desired Sb-Pd ratio. The synthesized electrocatalyst can be used as an anode catalyst for the methanol oxidation reaction (MOR), a prime fuel for direct methanol fuel cells (DEFCs). A morphological analysis of the Sb, Pd, and Sb-Pd electrocatalysts was performed by scanning electron microscopy (SEM) technique. The electrochemical properties of the Pd and Sb-Pd catalysts were evaluated using cyclic voltammetry (CV) and chronoamperometry (CA) in an alkaline electrolyte containing Na⁺ or Li⁺ cations. Compared to Pd alone, the Sb-Pd catalyst showed a twofold increase in peak current density and improved MOR kinetics. Both investigated catalysts exhibited higher poisoning tolerance in the solution containing Na⁺, implying that the product distribution in MOR depends on the alkali metal cation of the supporting electrolyte. The peak current of MOR at Pd and Sb‒Pd catalysts in the solution with Li⁺ cations is 1.4 times higher compared to the values obtained in the solution with Na⁺ cations, indicating the impact of the nature of alkali metal cations which arises from the formation of OH_ad ‒ cation clusters and the electronic interaction between CO_ad and OH_ad ‒ cation clusters. The presence of Sb in the structure of the bimetallic catalyst provides a lower susceptibility to the poisoning and consequently enhances MOR performances regarding the Pd catalyst.

Graphical Abstract