Iridium Deposited on Niobium-Doped Titanium Dioxide (NbTiO) for High-Stability and Effective Oxygen Evolution Reaction (OER) Catalyst in Acidic Environment

Abstract

The state-of-the-art iridium-based catalyst, which is the trade-off between activity and durability during acidic OER, needs to be distributed on low-cost effective support materials for the economical utilization of electrolyzers.1 Normally, dopant is introduced into the oxide lattice structure in order to improve the conductivity of the support, which in turn can diminish the Iridium loading content. In this talk, niobium doped titanium dioxide (NbTiO), which is proved to have promising durability in acidic OER conditions, is applied for supported Ir-based catalyst. Based on the powder compression method for conductivity measurement,2 the resistivity of synthesized Nb-doped TiO2, with niobium content of 10 at. % (NbTiO10), is about tens times lower than the resistivity of anatase TiO2 (a.TiO2). Which, in turn brings to the 40 wt. % Ir/NbTiO10 the resistivity of millions times lower than 40 wt.% Ir/a.TiO2 and hundreds times lower than 50 wt.% Ir/a.TiO2. Moreover, by introducing an organic framework to the synthesis, support's surface area can be enlarged and its macroporous morphology can be modified. Various ex-situ methods, e.g. HR-STEM, XRD, and RDE, are used to investigate the influence of the distribution and oxidation state of the Ir-active phase on doped TiO2 support onto the performance of catalysts, before and after the acceleration stress test (AST). And in-situ methods, including ICP-MS coupling scanning flow cell and XAS, are also applied, in order to reveal the alternating of every single component in the catalytic system during OER and after the AST. The catalyst was then tested in electrolyzer to compare its performance with the commercial Elyst Umicore Catalyst. Reier, T.; Oezaslan, M.; Strasser, P., Electrocatalytic Oxygen Evolution Reaction (OER) on Ru, Ir, and Pt Catalysts: A Comparative Study of Nanoparticles and Bulk Materials. ACS Catalysis 2012, 2 (8), 1765-1772. Karimi, F.; Peppley, B. A., Metal Carbide and Oxide Supports for Iridium-Based Oxygen Evolution Reaction Electrocatalysts for Polymer-Electrolyte-Membrane Water Electrolysis. Electrochimica Acta 2017, 246, 654-670.