A highly stable potentiometric pH sensor based on single-phase perovskite BaIrO3 nanofibers

Abstract

In this study, single-phase perovskite BaIrO<inf>3</inf> nanofibers were synthesized by electrospinning and post-calcination with careful control of annealing atmosphere (10 sccm O<inf>2</inf> and 90 sccm He). The synthesized BaIrO<inf>3</inf> nanofibers were applied for potentiometric pH sensing of which performance was compared with that of single Ir-based oxides. Regardless of the reduced noble Ir content, BaIrO<inf>3</inf> nanofibers exhibited excellent sensitivity (super-Nernstian potential response of ca. −67 mV pH−1) and improved reversibility and stability even in very low and high pH regions compared to the nanofibers composed of Ir(0)/IrO<inf>2</inf> and those of pure rutile IrO<inf>2</inf>. In fact, BaIrO<inf>3</inf> nanofibers maintained very similar sensitivity for 18 weeks of tested period while Ir/IrO<inf>2</inf> and IrO<inf>2</inf> counterparts showed the significantly decreased sensitivities. In addition, BaIrO<inf>3</inf> nanofibers exhibited superior selectivity to hydrogen ion over alkaline metal ions (e.g., Na+ and K+). The observed outstanding pH sensing performance of BaIrO<inf>3</inf> was attributed to the sturdy perovskite structure based on strong connectivity between [IrO<inf>6</inf>] octahedron units. This study demonstrates the feasibility of perovskite BaIrO<inf>3</inf> as a pH sensing electrode material alternative to or even better than extensively studied Ir oxides. © 2025 Elsevier B.V.