Electrocatalytic performance of Pd-based electro-catalysts supported on CNTs for isopropanol and ethanol electro-oxidation in alkaline medium

Abstract

Palladium carbon nanotubes and palladium-niobium carbon nanotubes electro-catalysts were successfully prepared through the alcohol reduction method. The composition and morphology of the synthesized electro-catalysts were examined using different physicochemical characterization techniques such as Field Emission Scanning Electron Microscopy, High-Resolution Transmission Electron microscopy, and X-ray photoelectron spectroscopy. High-Resolution Transmission Electron microscopy revealed hollow tubular structures showing multi-walled carbon nanotubes with palladium-niobium nanoparticles deposited on their surface with an average particle size of 5.02 nm. The electrochemical behavior of palladium carbon nanotubes and palladium-niobium carbon nanotubes for isopropanol and ethanol electro-oxidation were investigated through cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy techniques. Palladium-niobium carbon nanotubes bimetallic electro-catalyst demonstrated better poisoning tolerance and the highest electrocatalytic activity through low Tafel slopes, low onset potentials, and fast charge transfer kinetics compared to palladium carbon nanotubes monometallic and the commercial palladium on carbon. The addition of niobium modified the structure of palladium through the electronic effect, weakening the binding strength of carbonaceous species on the surface of palladium and thus increasing its electrocatalytic activity. The obtained results provided essential insights into palladium-niobium carbon nanotubes as promising electro-catalysts for direct alcohol fuel cells.