Nanoporous platinum electrode grown on anodic aluminum oxide membrane: Fabrication, characterization, electrocatalytic activity toward reactive oxygen and nitrogen species

Highlights: • A new type of nanoporous platinum (NPt) electrode was fabricated on porous aluminum oxide membrane at the first time. • Electrocatalytic mechanisms of NPt electrode toward NO and nitroxyl were proposed, which depended on pH value of buffer. • NPt electrode exhibited three times larger catalytic current to O₂, NO and nitroxyl than those on nanofilm Pt electrode. - Abstract: A new type of nanoelectrode, nanoporous platinum (NPt) electrode was prepared on aluminum oxide membrane by thermal evaporation deposition. The morphology, conductivity and electrocatalytic activity of NPt electrode were characterized and compared with those of nanofilm-Pt electrode through scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques, respectively. SEM images showed that "nanocavities" observed in NPt electrode were actually 2-dimensional enclosures by linked nanoparticles. It was different from the conventional arrays of "nanocavities" formed on homogeneous metal films. EIS data indicated that NPt electrode possesses higher conductivity. Compared with that on nanofilm-Pt electrode (14.05 O·cm²), the impedance spectrum on NPt electrode exhibits a semicircle portion with much smaller diameters (1.24 O·cm² for NPt-100, 1.48 O·cm² for NPt-200). Meanwhile, the response sensitivity of NPt electrode to O₂ is 0.85 mA cm^-2, which is larger than that of nanofilm-Pt electrode (0.54 mA cm^-2). The largest catalytic current for nitric oxide (NO) was obtained in buffer with pH value of 9.4 while for Angeli^'s salt (AS) was obtained in buffer with pH value of 5.4. Additionally, electrocatalytic mechanisms of NPt electrode toward NO and AS were proposed, which indicating it depended on pH value of buffer solution.