The technical issue of direct ethanol fuel cells is slow kinetics and low CO2 selectivity of ethanol electrooxidation by using Pt. Silica embedded carbon nanofiber (SECNF) was prepared as a catalyst support to improve electrocatalytic characteristics. Catalysts were characterized by SEM and XRD. Electrochemical measurements were performed to analyze catalytic activity and electrochemical active surface area of Pt/SECNF. The mass activity of Pt/SECNF was twice as high that of Pt/carbon nanofiber. In contrast, the value of ECSA was almost constant for each nanofiber catalyst. However, too much SiO2 addition was not preferable in the viewpoint of specific resistance of the sample layer. The activity enhancement is attributed to the improvement of specific activity for Pt/SECNF by the interaction between Pt and SiO2.
The technical issue of direct ethanol fuel cells is slow kinetics of ethanol electrooxidation by using noble metals such as Pt. We propose silica-embedded carbon nanofiber (SECNF) as a catalyst support for the electrooxidation of ethanol to improve catalytic activity of Pt. SECNF was prepared by electrospinning, then Pt nanoparticles were deposited on SECNF. Catalyst characterizations were performed by SEM, EDX, and XRD. Cyclic voltammetry was performed to analyze catalytic activity of Pt/SECNF. The mass activity of Pt/SECNF was 2.9 times higher than a commercially available Pt/carbon catalyst (Pt/Ccom). Electrochemically active surface area of Pt/SECNF was lower than Pt/Ccom. Hence, the activity enhancement is attributed to the improvement of specific activity for Pt/SECNF. This enhancement is attributed to the interaction between Pt and SiO2 like hydrogen spillover. Pt/SECNF is a promising catalyst for direct ethanol fuel cells which can reduce Pt loading.
The degradation of current density by impurities in bioethanol from lignocellulosic biomass for use in a direct ethanol fuel cell was evaluated. The degradation experiment of using a single cell was conducted by adding nine impurities, i.e., methanol, acetaldehyde, acetic acid, 1-propanol, allyl alcohol, ethyl acetate, 3-methyl-1-butanol, acetal (acetaldehyde diethyl acetal), and benzaldehyde, to a 2 M ethanol aqueous solution. The current density of the single cell was degraded by the quasi bioethanol including the nine impurities. To clarify the principal poisoning impurity, we performed the cell measurement by only adding each single impurity. As a result, allyl alcohol turned out to be the main catalyst poison under the estimated condition. The negative effects by the other impurities were almost negligible.
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