Abstract
Direct ethanol fuel cells (DEFCs) is receiving enormous attention as alternative electrical energy conversion systems. This paper gives an outline on some recent advances achieved in our laboratory regarding the development of high performing anode for ethanol oxidation. We developed multi-components binderless hierarchically organized layer onto layer nanostructured catalysts comprising a carbon paper (CP, current collector)/carbon nanotubes (CNTs, conductivity enhancer)/catalyst promoter (MOx, M: Sn; Ce)/Pt-based (electrocatalyst). The main focus was how to lower the onset oxidation potential (OOP) of ethanol at Pt75Sn25 catalyst. Towards that aim, metal oxides such as CeO2 and SnO2 were sought as catalyst promoters. It has been discovered that intercalating a nanostructured layer of SnO2 between CNTs and Pt75Sn25 considerably lowered the OOP of ethanol and also increased the specific mass activity (SMA) at low potentials. Indeed, the OOP at the CP/CNT/SnO2/Pt75Sn25 was 210 mV and 117 mV negative relative to that delivered by CP/CNT/Pt and CP/CNT/Pt75Sn25, respectively confirming by that the promoting effect of SnO2 of the oxidation of CO at low potentials. The SMA determined at slow potential scan rate of 5 mV/s at 0.4 V vs. Ag/AgCl revealed that CP/CNT/SnO2/Pt75Sn25 delivered an SMA of 1.2 times higher than that of the CP/CNT/Pt75Sn25 catalyst and 1.5 times greater than the one exhibited by the CP/CNT/CeO2/Pt75Sn25 catalyst.
Highlights
Ethanol is attractive as a biomass product, safe with high theoretical energy density (8.0 kWh kg-1) [1] and could make direct ethanol fuel cells (DEFCs) beneficial low-emission power sources
In our continuous effort to improve the catalytic performance of CNT/Pt75Sn25 electrode with the principal objective of lowering further the oxidation potential (OOP) of ethanol, the first part of this paper presents for the first time the synthesis, characterization and electroactivity towards ethanol oxidation reaction (EOR) of a CP/CNTs/CeO2/Pt75Sn25 nanostructured lol catalyst
Based on the information gained, at the end, we present our opinion on the future directions to follow for a better design of efficient anode materials for DEFC
Summary
Ethanol is attractive as a biomass product, safe with high theoretical energy density (8.0 kWh kg-1) [1] and could make direct ethanol fuel cells (DEFCs) beneficial low-emission power sources. The multifunctional requirements of catalysts for the direct oxidation of ethanol which include the ability to activate C-H, CO and C-C bonds, suggest that optimum performance will require ternary or even quaternary catalysts that oxidize ethanol at low potentials and demonstrate current densities higher than those of pure Pt. preparation of three or four components electrocatalyst is tedious and require the optimisation of the composition of each component plus the content of carbon additive, a necessary conductivity enhancer in fuel cells electrodes. Preparation of three or four components electrocatalyst is tedious and require the optimisation of the composition of each component plus the content of carbon additive, a necessary conductivity enhancer in fuel cells electrodes Such approach will necessitate an impressive number of synthesis experiments as well as the high cost that this entails. Taking into account the direct electrooxidation of ethanol in the fuel cells, the catalysts that could promote ethanol entire oxidation and displace the onset oxidation potential (OOP) to lower values are of the most importance
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