Galvanostatic Electrodeposition of Durable IrO_x Films on Low-Iridium-Supported Titanium for an Acidic Oxygen Evolution Reaction

Abstract

Ensuring or even optimizing the activity and stability of iridium oxide-coated titanium anodes while reducing the amount of iridium is still practically significant. In this work, IrO x -Ti electrodes are prepared by galvanostatic deposition at different deposition current densities and times. The iridium loading level, morphology, microstructure, and element composition distribution of these obtained electrodes are characterized, and their cyclic voltammetry and accelerated life tests were carried out in 0.5 M H2SO4 to investigate their electrochemical performance for the acidic oxygen evolution reaction (OER). For a better understanding of the anodic electrodeposition mechanism, a competing mechanistic hypothesis was proposed to describe the reactions and their relationship involved in this process. The results show that the IrO x electrodes electrodeposited at 0.1 mA cm–2 exhibited a superior performance for the OER in terms of stability. Especially, the electrode electrodeposited for 5 h (0.1 mA cm–2) demonstrated a long-term durability for 73.14 h (equivalent to at least 14,642 h, i.e., 610 days, in actual lifetime) with 1.0 mg cm–2 iridium loading. Simultaneously, a mathematical model was used to fit the relationship between accelerated lifetime and deposition current and iridium loading. This research provides some valuable insights into how to optimally use Ir as an OER electrocatalyst.

Observing Local pH Changes Using a Rotating Ring-Disk Electrode Functionalized with a Potentiometric pH-Sensing Probe

“…Similar, yet significantly smaller magnitude, redox features are observed for alkaline IrO x deposition on bare GC. In acidic conditions, the CVs exhibit comparatively minimal redox changes, with the exception of the Faradaic oxidation current observed at the highest potentials for the IrO x deposited on Au-coated GC, likely corresponding to water oxidation . To gain insights into the thermodynamic stability of various iridium species for the deposition conditions in this study, we refer to an iridium Pourbaix diagram.…”

“…In acidic conditions, the CVs exhibit comparatively minimal redox changes, with the exception of the Faradaic oxidation current observed at the highest potentials for the IrO x deposited on Au-coated GC, likely corresponding to water oxidation. 61 To gain insights into the thermodynamic stability of various iridium species for the deposition conditions in this study, we refer to an iridium Pourbaix diagram. Under the CV deposition conditions used in this study, IrO 2 is predicted to be the dominant iridium species present for both the alkaline and acidic solution baths.…”

A Study on the Triangular-Wave Electrodeposition of Iridium Oxide on Ti

“…12,13 Electrodeposition of metal oxides has mild conditions, and the deposited particles are uniform, fine and dense; the shape and thickness of the electrodes can be adjusted by experiments. [14][15][16][17] Compared with crystalline iridium oxide obtained by thermal decomposiiton, electrodeposited iridium oxide is amorphous or mixed crystalline phase, which can provide appropriate binding energies of oxygen intermidiates and reduce the reaction energy barrier, enhancing electrocatalytic activity for OER. 16,[18][19][20] Currently reported electrodeposiiton methods include potentiostatic, galvanostatic, and cyclic voltemtric electrodeposiiton, etc.…”

“…16,[18][19][20] Currently reported electrodeposiiton methods include potentiostatic, galvanostatic, and cyclic voltemtric electrodeposiiton, etc. Our previous report investigated the effect of current density and deposition time of galvanostatic electrodeposition on the performance of IrOx electrodes, 15 which showed that IrO x prepared at lower current density had superior catalytic activity and duriability. Although potentiostatic and galvanostatic electrodepostion have advantages of simple operation and controllable process, the iridium oxide deposition layer prepared by cyclic voltammetry electrodeposition has high uniformity, fine grains, easy film formation, better electrocatalytic activity and longer continuous oxygen evolution ability.…”