Impact of Ir-Valence Control and Surface Nanostructure on Oxygen Evolution Reaction over a Highly Efficient Ir–TiO2 Nanorod Catalyst

• Published in: ACS catalysis Vol. 9; no. 8; pp. 6974 - 6986
• Main Authors: Cheng, Junfang, Yang, Jun, Kitano, Sho, Juhasz, Gergely, Higashi, Manabu, Sadakiyo, Masaaki, Kato, Kenichi, Yoshioka, Satoru, Sugiyama, Takeharu, Yamauchi, Miho, Nakashima, Naotoshi
• Format: Journal Article
• Language: English
• Published: American Chemical Society 02.08.2019
• Subjects: iridium-valence-engineering; oxygen evolution reaction (OER); in situ electrochemical XANES and EXAFS; Ir-oxide catalyst
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.9b01438

Iridium oxide (IrO x )-based materials are the most suitable oxygen evolution reaction (OER) catalysts for water electrolysis in acidic media. There is a strong demand from industry for improved performance and reduction of the Ir amount. Here, we report a composite catalyst, IrO x –TiO2–Ti (ITOT), with a high concentration of active OH species and mixed valence IrO x on its surface. We have discovered that the obtained ITOT catalyst shows an outstanding OER activity (1.43 V vs RHE at 10 mA cm–2) in acidic media. Moreover, no apparent potential increase was observed even after a chronopotentiometry test at 10 mA cm–2 for 100 h and cyclic voltammetry for 700 cycles. We proposed a detailed OER mechanism on the basis of the analysis of the in situ electrochemical X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements as well as density functional theory (DFT) calculations. All together, we have concluded that controllable Ir-valence and the high OH concentration in the catalyst is crucial for the obtained high OER activity.