Sustainable Recovery of Iridium Oxide Waste to Electrospun IrOx Nanofibers with Tunable Electrochemical Sensing Properties

Iridium oxide is highly valued for its exceptional chemical inertness, electrical conductivity, and biocompatibility. However, the scarcity and associated high cost of iridium present significant challenges, compounded by the difficulty of recycling due to its chemical stability. We have developed an innovative electrochemical method for the reduction of iridium-containing waste solutions, characterized by minimal environmental impact, high selectivity for iridium, and efficient recovery rates.
This method utilizes sequential chlorination and electrochemical reduction processes to transform iridium oxide nanoparticles from waste into the soluble Ir(III) species IrCl₆^3-, suitable as a precursor for electrospinning. The iridium oxide nanoparticles are initially treated with 36 wt% hydrochloric acid at 70°C for 18 hours, yielding IrCl₆^2- with a pH of 0.3. This species is subsequently reduced to IrCl₆^3- at a reduction potential of 0.6 V versus SCE. The regenerated Ir³⁺ serves as a precursor in the electrospinning process, producing high-performance iridium oxide nanofibers.
These nanofibers exhibit tunable performance in applications involving the electrochemical reduction of H₂O₂ and the oxidation of dopamine, contingent upon post-annealing temperature control. The IrOx nanofibers demonstrate a broad linear response range from 1 to 1000 μM for H₂O₂ detection, with a low detection limit (LOD) of 25 μM and impressive sensitivity of 392 μA/μMcm². Additionally, these iridium oxide nanofibers show exceptional sensitivity to dopamine, achieving 2.76 μA/μMcm² with an LOD of 145.16 nM, indicating their suitability for electrochemical sensing applications.