Interest in sustainable and renewable energy sources has grown dramatically as a result in the negative effects fossil fuels have on the environment and the dangers of their depletion. In this regard, hydrogen energy has become a viable choice for sustainable and ecologically friendly energy generation. However, there are still many technical obstacles in the way of safely transporting and storing hydrogen. As a result of their high efficiency, low emissions, and secure operating conditions, fuel cells have become growing in popularity among alternative energy systems. Liquid fuels such as methanol and sodium borohydride, used in fuel cells, are particularly attractive for direct liquid fuel cells (DLFCs) owing to their high energy density and hydrogen storage capacity. This study examines the electrochemical properties influencing the usability of methanol and sodium borohydride in DLFCs using cyclic voltammetry (CV). Voltammetric data were analyzed to derive reaction rate expressions. Systematic measurements were conducted using platinum and gold working electrodes in an alkaline NaOH (sodium hydroxide) medium. To assess the effect of fuel concentration, the electrolyte concentration was fixed at 0.1 M NaOH, while experiments were performed with methanol (0.05–1 M) and sodium borohydride (0.0002–0.01 M). A scan rate of 0.01 V/s was determined to provide the optimal observation range for both fuels. To investigate the effect of electrolyte concentration, the fuel concentration was held constant (0.05 M for methanol, 0.0002 M for sodium borohydride), while varying NaOH concentrations were evaluated. In all systems, distinct anodic currents were observed at the working electrodes, with oxidation peak currents increasing alongside higher fuel and electrolyte concentrations. Cyclic voltammetry analysis enabled derivation of the reaction kinetics for both fuel systems. The methanol oxidation reaction followed the rate expression j = k0[NaOH]0,15[CH3OH]0,38e(nFE/RT), while sodium borohydride oxidation exhibited j = k0[NaOH]0,21[NaBH4]0,57e(nFE/RT. These quantitative relationships reveal that the electrochemical oxidation rates for both fuels display greater dependence on fuel concentration than on electrolyte concentration. This kinetic analysis provides fundamental insights into the operational optimization of direct methanol fuel cell and direct sodium borohydride fuel cell.

Investigating the reaction rate expressions of methanol and sodium borohydride via cyclic voltammetry

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发表日期：

2025年12月29日

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Eda Nur Asileren,
Sena Nur Gülbaş,
Merve Gördesel Yildiz

摘要

Interest in sustainable and renewable energy sources has grown dramatically as a result in the negative effects fossil fuels have on the environment and the dangers of their depletion. In this regard, hydrogen energy has become a viable choice for sustainable and ecologically friendly energy generation. However, there are still many technical obstacles in the way of safely transporting and storing hydrogen. As a result of their high efficiency, low emissions, and secure operating conditions, fuel cells have become growing in popularity among alternative energy systems. Liquid fuels such as methanol and sodium borohydride, used in fuel cells, are particularly attractive for direct liquid fuel cells (DLFCs) owing to their high energy density and hydrogen storage capacity. This study examines the electrochemical properties influencing the usability of methanol and sodium borohydride in DLFCs using cyclic voltammetry (CV). Voltammetric data were analyzed to derive reaction rate expressions. Systematic measurements were conducted using platinum and gold working electrodes in an alkaline NaOH (sodium hydroxide) medium. To assess the effect of fuel concentration, the electrolyte concentration was fixed at 0.1 M NaOH, while experiments were performed with methanol (0.05–1 M) and sodium borohydride (0.0002–0.01 M). A scan rate of 0.01 V/s was determined to provide the optimal observation range for both fuels. To investigate the effect of electrolyte concentration, the fuel concentration was held constant (0.05 M for methanol, 0.0002 M for sodium borohydride), while varying NaOH concentrations were evaluated. In all systems, distinct anodic currents were observed at the working electrodes, with oxidation peak currents increasing alongside higher fuel and electrolyte concentrations. Cyclic voltammetry analysis enabled derivation of the reaction kinetics for both fuel systems. The methanol oxidation reaction followed the rate expression j = k₀[NaOH]^0,15[CH₃OH]^0,38e^(nFE/RT), while sodium borohydride oxidation exhibited j = k₀[NaOH]^0,21[NaBH₄]^0,57e^(nFE/RT. These quantitative relationships reveal that the electrochemical oxidation rates for both fuels display greater dependence on fuel concentration than on electrolyte concentration. This kinetic analysis provides fundamental insights into the operational optimization of direct methanol fuel cell and direct sodium borohydride fuel cell.