(360b) Anodically Grown Pt(II) Oxide Microelectrode/Nanoelectrode pH Sensor

Platinum electrode availability in electrochemical laboratories makes it attractive as a potentiometric solid-state pH sensor for aqueous solutions. However, challenges have been reported in fabricating anodic-grown platinum oxide potentiometric pH sensors. In this work, cyclic voltammetry in 0.5 M H₂SO₄ and 1 M NaOH was conducted to assess the effect of acidic and basic solutions on the anodic-grown platinum (II) oxide for designing Pt/Pt(II) oxide pH sensor. Chronoamperometry was also employed to grow a platinum (II) oxide layer on an ultramicroelectrode in both solutions, followed by measuring their potentiometric response in various pH solutions. The platinum (II) oxide manufactured in 1 M NaOH showed a close Nernstian response (~ -60 mV/pH), and was insensitive to dissolved oxygen, cation and anion identities, and molar ionic strength. When the platinum (II) oxide was grown on a platinum nanoelectrode, the response time was ~ 2 seconds for an approximately twelve-fold pH step change. These findings highlight the importance of the solution pH used during platinum oxidation on anodic platinum (II) oxide properties in sensing solution pH. The straightforward approach used in this work for fabricating Pt/PtO microelectrode/nanoelectrode pH sensors by direct oxidation can ease real-time pH measurement in complex aqueous environments.