Fast microwave-assisted solvothermal synthesis of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated MWCNTs: Pd-based bimetallic catalysts for ethanol oxidation in alkaline medium

Abstract

The preparation of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated multi-walled carbon nanotubes (SF-MWCNTs) using a very rapid microwave-assisted solvothermal strategy has been described. Electrocatalytic behaviour of the SF-MWCNT-Pd and its "mixed" bimetallic electrocatalysts (i.e., SF-MWCNT-PdSn mix and SF-MWCNT-PdNi) towards ethanol oxidation in alkaline medium was investigated. The result shows that the mixed Pd-based catalysts (obtained by simple ultrasonic-mixing of the individual MWCNT-metal nanocomposites) gave better electrocatalytic activity than their alloy nanoparticles (obtained by co-reduction of metal salts) or Pd alone. The SF-MWCNT platform gave better electrocatalytic performance compared to the unsulfonated and commercial Vulcan carbons. Detailed electrochemical studies (involving cyclic voltammetry, chronoamperometry, chronopotentiometry, and impedance spectroscopy) prove that the mix electrocatalytic oxidation of ethanol at the platform is more stable, ours at lower potential, gives lower Tafel slopes, with faster charge-transfer kinetics compared to its SF-MWCNT-PdSn mix SF-MWCNT-PdNi counterpart. Also, result revealed that SF-MWCNT-PdNi is more tolerant to CO poisoning than the SF-MWCNT-PdSn. The results provide some important insights into the electrochemical response of microwave-synthesised Pd-based bimetallic catalysts for potential application in direct ethanol alkaline fuel cell technology.