Nanoporous electrodes are representative electrode materials for diverse applications, such as energy conversion devices and sensors. Recently, selectivity based on the size of ions arising from nanoporous structures has been applied to capacitive deionization, electrochemical supercapacitors, and conductometry. Herein, we explored the selectivity based on the size of the redox molecules on the electrochemical reaction at the nanoporous Pt electrode with extremely small (1-2 nm) and uniform pores by linear sweep voltammetry and AC impedance spectroscopy. Among primary alcohols with sizes smaller than that of the pores, we observed exceptional selective enhancement in the case of methanol due to its smallest size, despite all the alcohols having a similar reaction mechanism. These findings may provide an insight into electrochemical analysis and electrocatalysis based on nanoporous structures.Devices based on electrochemical principles, such as energyconversion devices (for example, batteries, supercapacitors, fuel cells, and solar cells) and chemical/bio sensors are ubiquitous. The performance of these devices depends on the properties of the electrodes. Rapid advances in nanoscience and nanotechnology have led to an increased interest in nanoscale electrochemistry to improve the performance of these devices. Recently, nanoporous electrodes have been extensively utilized in the fields of energy conversion, sensors, and catalysts owing to their high surface-to-volume ratio. [1] More recently, the effect
Nanoporous electrodes with extremely small pores have been developed for improved supercapacitors and electroanalysis. Ion transport into nanoconfined spaces has been studied using nanoporous carbon. Herein, we explore the size effect and hydrophobicity of ions on the charging dynamics using microporous Pt by cyclic voltammetry and electrochemical impedance spectroscopy. As the size of the effective hydrated ions decreased, the capacitance increased, and the movement of ions into and within the nanopores was less restricted. The effect of ionic size was more pronounced for hydrophobic organic cations than for hydrophilic alkali cations in microporous Pt. In addition, the microporous Pt electrode exhibited better performance in terms of capacitance and charging dynamics than the mesoporous carbon electrode when the hydrophilic electrolyte is dissolved in an aqueous solution. These findings provide insight into the formation of an electrical double layer at microporous metal electrodes and their applications in supercapacitors, electrocatalysts, and electroanalysis.
The Cover Feature illustrates selective enhancement of methanol electrooxidation in the ultra‐compact nanoporous Pt electrode. Methanol is smaller than 1‐propanol so that it can penetrate deeper into the nanopores. It is essential to consider the size of the reactive species at nanoporous electrodes. More information can be found in the Communication by J. J. Bang et al.
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