Electroactivation-induced IrNi nanoparticles under different pH conditions for neutral water oxidation

Woong Hee Lee, Jaekyung Yi, Hong Nhan Nong, Peter Strasser, Keun Hwa Chae, Byoung Koun Min, Yun Jeong Hwang, Hyung Suk Oh

Research output: Contribution to journalArticlepeer-review

Abstract

Electrochemical oxidation processes can affect the electronic structure and activate the catalytic performance of precious-metal and transition-metal based catalysts for the oxygen evolution reaction (OER). Also there are emerging requirements to develop OER electrocatalysts under various pH conditions in order to couple with different reduction reactions. Herein, we studied the effect of pH on the electroactivation of IrNi alloy nanoparticles supported on carbon (IrNi/C) and evaluated the electrocatalytic activities of the activated IrNiOx/C for water oxidation under neutral conditions. In addition, their electronic structures and atomic arrangement were analyzed by in situ/operando X-ray absorption spectroscopy (XAS) and identical location transmission electron microscopy techniques, showing the reconstruction of the metal elements during electroactivation due to their different stabilities depending on the electrolyte pH. IrNiOx/C activated under neutral pH conditions showed a mildly oxidized thin IrOx shell. Meanwhile, IrNiOx/C activated in acidic and alkaline electrolytes showed Ni-leached IrOx and Ni-rich IrNiOx surfaces, respectively. Particularly, the surface of IrNiOx/C activated under alkaline conditions shows IrOx with a high d-band hole and NiOx with a high oxidation state leading to excellent OER catalytic activity in neutral media (η = 384 mV at 10 mA cm-2) whereas much lower OER activity was reported under alkaline or acid conditions. Our results, which showed that electrochemically activated catalysts under different pH conditions exhibit a unique electronic structure by modifying the initial alloy catalyst, can be applied for the design of catalysts suitable for various electrochemical reactions.

Original languageEnglish
Pages (from-to)14903-14910
Number of pages8
JournalNanoscale
Volume12
Issue number27
DOIs
Publication statusPublished - 2020 Jul 21

ASJC Scopus subject areas

  • Materials Science(all)

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