Development of Metal/Metal Oxide Nanostructures-Based Anodes for the Electro-Oxidation of Ethylene Glycol for Fuel Cell Applications

Abstract

A set of propitious catalysts were developed for ethylene glycol electrooxidation (EGO), the primary anodic reaction in Direct EG fuel cells (DEGFCs). In the course of development, a glassy carbon (GC) substrate was modified sequentially and electrochemically with several layers; one of which had to be platinum nanoparticles (nano-Pt). The other layers included one or two layers of several transition metal (Ni, Mn and Co) oxide nanostructures (e.g., nano-NiOx, nano-MnOx and nano-CoOx). The loading level and sequence of the catalyst ingredients impacted to a great extent the catalytic activity of EGO where nano-Pt was optimized in the most inner layer directly on top of the GC substrate. Several other parameters including the operating pH and temperature and scan rate during EGO were optimized. Detailed morphological, compositional and structural inspections of the as-prepared catalysts were provided using FE-SEM, EDS and XRD while HPLC assisted in the detection of the products of EGO. Interestingly, the highest catalytic activity and stability toward EGO were achieved at the CoOx/NiOx/Pt/GC catalyst (with this deposition sequence). For the first time, we could successfully probe the EGO electrodynamically at the CoOx/NiOx/Pt/GC catalyst; capacitance measurements provided important information about the reaction mechanism. In alkaline medium, the maximum capacitance (Cmax) and the direct oxidation peak current (Ip) of the CoOx/NiOx/Pt/GC catalyst during EGO coincided at the same potential. Moreover, the catalyst’s capacitance was influenced by the nature and loading of intermediates and products released during EGO. The thesis extended to investigate the synergism in the catalytic activity at the Pt/GC catalyst upon fuel blending (e.g., EG/MeOH and EG/EtOH). Molar ratios of 1:1 for EG:MeOH and 1:0.2 for EG:EtOH were found optimum in this investigation and therefore, were tested for the whole set of developed catalysts.