IrO 2 Oxygen Evolution Catalysts Prepared by an Optimized Photodeposition Process on TiO 2 Substrates.

Preparing high-performance oxygen evolution reaction (OER) catalysts with low precious metal loadings for water electrolysis applications (e.g., for green hydrogen production) is challenging and requires electrically conductive, high-surface-area, and stable support materials. Combining the properties of stable TiO 2 with those of active iridium oxide, we synthesized highly active electrodes for OER in acidic media. TiO 2 powders (both commercially available Degussa P-25 ® and hydrothermally prepared in the laboratory from TiOSO 4 , either as received/prepared or following ammonolysis to be converted to titania black), were decorated with IrO 2 by UV photodeposition from Ir(III) aqueous solutions of varied methanol scavenger concentrations. TEM, EDS, FESEM, XPS, and XRD measurements demonstrate that the optimized version of the photodeposition preparation method (i.e., with no added methanol) leads to direct deposition of well-dispersed IrO 2 nanoparticles. The electroactive surface area and electrocatalytic performance towards OER of these catalysts have been evaluated by cyclic voltammetry (CV), Linear Sweep Voltammetry (LSV), and Electrochemical Impedance Spectroscopy (EIS) in 0.1 M HClO 4 solutions. All TiO 2 -based catalysts exhibited better mass-specific (as well as intrinsic) OER activity than commercial unsupported IrO 2 , with the best of them (IrO 2 on Degussa P-25 ® ΤiO 2 and laboratory-made TiO 2 black) showing 100 mAmg Ir -1 at an overpotential of η = 243 mV. Chronoamperometry (CA) experiments also proved good medium-term stability of the optimum IrO 2 /TiO 2 electrodes during OER.