title: In Operando Identification of Geometrical-Site-Dependent Water Oxidation Activity of Spinel Co3O4.
abstract: Spinel Co3O4, comprising two types of cobalt ions: one Co(2+) in the tetrahedral site (Co(2+)(Td)) and the other two Co(3+) in the octahedral site (Co(3+)(Oh)), has been widely explored as a promising oxygen evolution reaction (OER) catalyst for water electrolysis. However, the roles of two geometrical cobalt ions toward the OER have remained elusive. Here, we investigated the geometrical-site-dependent OER activity of Co3O4 catalyst by substituting Co(2+)(Td) and Co(3+)(Oh) with inactive Zn(2+) and Al(3+), respectively. Following a thorough in operando analysis by electrochemical impedance spectroscopy and X-ray absorption spectroscopy, it was revealed that Co(2+)Td site is responsible for the formation of cobalt oxyhydroxide (CoOOH), which acted as the active site for water oxidation.
authors.affiliation: School of Chemical and Biomedical Engineering, Nanyang Technological University , Block N1.2, 62 Nanyang Drive, Singapore 637459, Singapore.
authors.forename: Hsin-Yi
authors.initials: HY
authors.lastname: Wang
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei, 106, Taiwan, Republic of China.
authors.forename: Sung-Fu
authors.initials: SF
authors.lastname: Hung
authors.affiliation: TUM CREATE , 1 CREATE Way, #10-02 CREATE Tower, Singapore 138602, Singapore.
authors.forename: Han-Yi
authors.initials: HY
authors.lastname: Chen
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 300, Taiwan, Republic of China.
authors.forename: Ting-Shan
authors.initials: TS
authors.lastname: Chan
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei, 106, Taiwan, Republic of China.
authors.forename: Hao Ming
authors.initials: HM
authors.lastname: Chen
authors.affiliation: School of Chemical and Biomedical Engineering, Nanyang Technological University , Block N1.2, 62 Nanyang Drive, Singapore 637459, Singapore.
authors.forename: Bin
authors.initials: B
authors.lastname: Liu