Abstract
A novel non-precious multiwalled carbon nanotubes (CNTs)—supported metal oxide electrocatalyst was developed for methanol electrooxidation in alkaline medium. The catalyst was fabricated by simultaneous electrodeposition of copper-cobalt-nickel ternary nanostructures (CuCoNi) on a glassy carbon electrode (GCE) modified with CNTs. The proposed electrode was characterized using X-ray diffraction (XRD), energy dispersive X-ray (EDX), and scanning electron microscopy (SEM). The electrochemical behavior and the electrocatalytic performance of the suggested electrode towards the oxidation of methanol were evaluated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA) in alkaline medium. Several parameters were investigated, e.g., deposition time, potential scan rate, etc. Compared to Cu, Co, or Ni mono electrocatalysts, the electrode based on ternary-metals exhibited superior electrocatalytic activity and stability towards methanol electrooxidation. For instance, CuCoNi@CNTs/GCE has shown at least 2.5 times electrocatalytic activity and stability compared to the mono eletrocatalysts. Moreover, the present study found that the optimized loading level is 1500 s of simultaneous electrodeposition. At this loading level, it was found that the relation between the Ip/ν1/2 function and scan rate gives the characteristic features of a catalytic process. The enhanced activity and stability of CuCoNi@CNTs/GCE was attributed to (i) a synergism between three metal oxides coexisting in the same structure; (ii) the presence of CNTs as a support for the metal oxides, that offers high surface area for the deposited tertiary alloy and suppresses the aggregation and sintering of the metals oxide with time; as well as (iii) the increase of the conductivity of the deposited semiconducting metal oxides.
Highlights
Owing to the world energy crisis and fossil fuels depletion, the development of renewable alternative energy sources and technologies such as fuel cells (FCs), solar cells, and wind energy are presently being researched throughout the world [1]
The electrooxidation of methanol is considered the key step in direct methanol fuel cells (DMFCs) in both alkaline and acidic fuel cells, and the commercialization of DMFCs is limited in part by the durability, scarcity, and high cost of the Pt-based methanol electrooxidation catalysts [5,6]
The purpose of the present work is to fabricate a ternary catalyst composed of NiOx, CuOx, and CoOx modified carbon nanotubes (CNTs)/glassy carbon electrode (GCE) and determine their electrocatalytic activity towards methanol oxidation in alkaline medium at different deposition times
Summary
Owing to the world energy crisis and fossil fuels depletion, the development of renewable alternative energy sources and technologies such as fuel cells (FCs), solar cells, and wind energy are presently being researched throughout the world [1]. FCs have received much attention recently due to their great range of benefits, for example high efficiencies, low emission, and fuel flexibility [2,3,4]. Sci. 2017, 7, 64 methanol, ethanol, and glucose [2,3,4]. Methanol as a fuel has many advantages over H2 such as low-cost, availability, ease of storage, and transport. Direct methanol fuel cells (DMFCs) are considered as one of the best choices for future clean energy sources [5,6]. The electrooxidation of methanol is considered the key step in DMFCs in both alkaline and acidic fuel cells, and the commercialization of DMFCs is limited in part by the durability, scarcity, and high cost of the Pt-based methanol electrooxidation catalysts [5,6]
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