In Situ/ Operando Soft X-ray Spectroscopic Identification of a Co4+Intermediate in the Oxygen Evolution Reaction of Defective Co3O4Nanosheets

Yu Cheng Huang, Wei Chen, Zhaohui Xiao, Zhiwei Hu, Ying Rui Lu, Jeng Lung Chen, Chi Liang Chen, Hong Ji Lin, Chien Te Chen, K. Thanigai Arul, Shuangyin Wang*, Chung Li Dong*, Wu Ching Chou*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Defect engineering is an important means of improving the electrochemical performance of the Co3O4electrocatalyst in the oxygen evolution reaction (OER). In this study, operando soft X-ray absorption spectroscopy (SXAS) is used to explore the electronic structure of Co3O4under OER for the first time. The defect-rich Co3O4(D-Co3O4) has a Co2.45+state with Co2+at both octahedral (Oh) and tetrahedral (Td) sites and Co3+at Oh, whereas Co3O4has Co2.6+with Co2+and Co3+at Tdand Ohsites, respectively. SXAS reveals that upon increasing the voltage, the Co2+in D-Co3O4is converted to low-spin Co3+, some of which is further converted to low-spin Co4+most Co2+in Co3O4is converted to Co3+but rarely to Co4+. When the voltage is switched off, Co4+intermediates quickly disappear. These findings reveal Co(Oh) in D-Co3O4can be rapidly converted to active low-spin Co4+under operando conditions, which cannot be observed by ex situ XAS.

Original languageEnglish
Pages (from-to)8386-8396
Number of pages11
JournalJournal of Physical Chemistry Letters
Volume13
Issue number35
DOIs
StatePublished - 8 Sep 2022

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