DOI: 10.5061/dryad.bg79cnpjc
title: Atomically dispersed hexavalent iridium oxide from MnO2 reduction for oxygen evolution catalysis

description: Hexavalent iridium (IrVI) oxide is predicted to be more active and stable
 than any other Ir oxide for the oxygen evolution reaction in acid;
 however, its experimental realization remains challenging. Here, we report
 the synthesis, characterization, and application of atomically dispersed
 IrVI oxide (IrVI-ado) for proton-exchange membrane (PEM) water
 electrolysis. The IrVI-ado was synthesized by oxidatively substituting the
 ligands of K2IrCl6 with manganese oxide. The mass-specific activity (1.7 ×
 105 A gIr-1) and turnover number (1.5 × 108) exceeded those of benchmark
 Ir oxides, and in-siu X-ray analysis during PEM operations manifested the
 durability of IrVI at current densities up to 2.3 A cm-2. The high
 activity and stability of IrVI-ado showcase its promise as an anode
 material for PEM electrolysis.
description: Nafion 115 polymer membranes were used to fabricate the membrane
 electrode assembly (MEA). Prior to use, the Nafion membrane was boiled
 sequentially for 1 h each in 3 wt.%
 H<sub>2</sub>O<sub>2</sub>, Milli-Q water, 1.0 M
 H<sub>2</sub>SO<sub>4</sub>, and Milli-Q water to
 remove possible contaminants and ensure that the membrane was completely
 protonated. Ir<sup>VI</sup><em>-ado</em> samples
 with loading amounts of 0.02, 0.04, and 0.08 mg<sub>Ir</sub>
 cm<sup>-2</sup> were used as an anode and coated with 10 wt. %
 Nafion ionomer before being assembled into the MEAs. Pt/C catalyst (20 wt%
 Pt on carbon black, Fuel Cell Earth) coated on hydrophobic carbon paper
 (TGP-H-060, Toray) with a loading amount of 0.2 mg<sub>Pt
 </sub>cm<sup>-2</sup> was used as a cathode. The Pt/C
 catalyst slurry used for coating was prepared by mixing Pt/C, water,
 ethanol, and Nafion solution (10 wt% in H<sub>2</sub>O,
 Sigma-Aldrich) with a Pt/C to Nafion ionomer ratio of 3:1. The MEAs with
 an active area of 1 cm<sup>2</sup> were prepared by
 hot-pressing the anode and cathode on a Nafion membranes at 135 °C at a
 mold clamping force of 2 MPa for 3 min. Electrolysis tests were conducted
 using a single-cell PEM electrolyzer (WE-4S-RICW, FC Development, Japan).
 The current-voltage and long-term durability were conducted using a
 potentiostat (HZ-7000, Hokuto Denko) equipped with a 30A-booster
 (HZAP1230, Hokuto Denko). All tests were conducted at 80 °C with water fed
 into the anode side of the PEM electrolyzer.
description: # Atomically dispersed hexavalent iridium oxide from MnO2 reduction for
 oxygen evolution catalysis
 [https://doi.org/10.5061/dryad.bg79cnpjc](https://doi.org/10.5061/dryad.bg79cnpjc) ## Description of the data and file structure Dataset1: Cell voltages of IrVI-*ado* in PEM cell with a mass-specific activity of 50000 A gIr-1. The dataset shows the variations in cell voltage (E) over time (t). Dataset2: Cell voltages of IrVI-*ado* in PEM cell with a mass-specific activity of 25000 A gIr-1. The dataset shows the variations in cell voltage (E) over time (t). Dataset3: Cell voltages of IrVI-*ado* in PEM cell with a mass-specific activity of 12500 A gIr-1. The dataset shows the variations in cell voltage (E) over time (t). Dataset4: Cell voltages of IrVI-*ado* in PEM cell with a mass-specific activity of 22500 A gIr-1. The dataset shows the variations in cell voltage (E) over time (t).