Efficient electrooxidation of ammonia using platinum supported on titania/sulfur-doped onion like carbon nanoparticles in direct ammonia fuel cells

Ludwe L. Sikeyi, Laercia R. Bila, Themba D. Ntuli, Cyril T. Selepe, Nobanathi W. Maxakato, Neil J. Coville, Manoko S. Maubane-Nkadimeng

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1 Citation (Scopus)

Abstract

This study reports on the synthesis of platinum supported on titania oxide nanoparticles decorated on sulfur doped onion-like carbon nanoparticles (S-OLCNs) as electrocatalysts for ammonia oxidation reactions in alkaline media. S-OLCNs (S = 1.6 %) were synthesized in a one-step flame pyrolysis method using thiophene as the starting material and titania nanoparticles were prepared using a microwave-assisted hydrolysis technique (5–10 % titania decoration). Pt/S-OLCN, Pt/TiO2 and Pt/TiO2/S-OLCN electrocatalysts (10 % Pt loading) were synthesized by the ethylene glycol assisted reduction method. Transmission electron microscopy studies confirmed the presence of well dispersed spherically shaped Pt NPs on the surface of the S-OLCN, TiO2 and TiO2/S-OLCN support materials (d = 1.93 ± 0.38 nm, 1.98 ± 0.79 nm, 2.13 ± 0.52 nm, respectively). XRD patterns confirmed the anatase phase for the titania. The Pt/S-OLCN, Pt/TiO2 and Pt/TiO2/S-OLCN and Pt/C electrocatalysts were investigated in the ammonia oxidation reaction (AOR). The existence of the well-dispersed TiO2 (and Pt) on the S-OLCNs gave rise to enhanced AOR catalytic performance when compared to Pt/S-OLCN, Pt/TiO2 and commercial 10 wt% Pt/C catalysts. Furthermore, the Pt/TiO2/S-OLCN electrocatalyst exhibited better long term stability and a faster charge transfer resistance than Pt/S-OLCN, Pt/TiO2 and commercial 10 wt% Pt/C electrocatalysts. These results indicate that the incorporation of TiO2 nanoparticles into Pt/S-OLCN is an effective strategy to improve the AOR activity of Pt by facilitating the electron transfer process during the catalytic reactions.

Original languageEnglish
Article number109612
JournalDiamond and Related Materials
Volume132
DOIs
Publication statusPublished - Feb 2023

Keywords

  • Ammonia oxidation reactions
  • Cyclic voltammetry
  • Nano-catalysts
  • Onion-like carbon nanoparticles
  • Sulfur doping

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • General Chemistry
  • Mechanical Engineering
  • Materials Chemistry
  • Electrical and Electronic Engineering

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