Experimental Verification of Ir 5d Orbital States and Atomic Structures in Highly Active Amorphous Iridium Oxide Catalysts
[1];
[2];
[5];
[1];
[8];
[9];
[10];
[11];
[11];
[10]
more »
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)
- Chung-Ang Univ., Seoul (South Korea)
- Pohang Univ. of Science and Technology (POSTECH) (South Korea); Inst. for Basic Science (IBS), Pohang (South Korea). Center for Artificial Low Dimensional Electronic Systems
- Pohang Accelerator Lab. (PAL) (Korea, Republic of)
- Ulsan National Inst. of Science and Technology (UNIST), Ulsan (South Korea)
- Argonne National Lab. (ANL), Lemont, IL (United States). Advanced Photon Source (APS)
- Stony Brook Univ., NY (United States). Joint Photon Sciences Inst.
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)
- Argonne National Lab. (ANL), Lemont, IL (United States)
- Yale Univ., New Haven, CT (United States)
In iridium oxide catalysts, the electronic states whose energies are in the range of energetics and charge transfer kinetics of the oxygen evolution reaction (OER) originate from the Ir 5d orbital states. However, the understanding of the atomic structures and orbital states underlying catalytic reactivity in amorphous iridium oxide oxygen evolving catalysts (Ir-OECs) is incomplete compared to that of crystalline oxides, owing to a lack of direct experimental verification. Here, we present experimental approaches using resonant inelastic X-ray scattering (RIXS) to directly access Ir 5d orbital excitations at the Ir L3 edge and atomic pair distribution function (PDF) measurements to characterize electronic and coordination structures at the atomic scale. The so-called iridium blue layer (IrBL) and IrOx were formed from the organometallic precursor complex [Cp*Ir(H2O)3]SO4 and the inorganic precursor IrCl3, respectively. Ex situ IrBL and IrOx films for RIXS and PDF measurements were prepared by conditioning electrodeposited films at a low voltage. The incident energy RIXS profile of IrOx exhibited extra weak resonantly enhanced excitation below 2 eV energy loss. The feature was clearly different from a single high-energy excitation above 3 eV of IrBL related to the interband transition between π- and σ-antibonding states. The atomic structure refinement based on PDF measurements revealed the atomic structure domains to have edge- and corner-shared IrO6 octahedra with trigonal-type distortion. Furthermore, density functional theory calculations guided by the refined atomic structures shed light on the electronic structure corresponding to experimental results, including insulating and metallic phases in ex situ IrBL and IrOx films, respectively. Our study establishes different Ir 5d orbital states and atomic structures in two amorphous Ir oxide OER catalysts in their reduction states.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); National Research Foundation of Korea (NRF)
- Grant/Contract Number:
- SC0012704; AC02-06CH11357; FG02-07ER15909; 2019K1A3A7A09033393; 2020R1C1C1012424
- OSTI ID:
- 1818935
- Alternate ID(s):
- OSTI ID: 1813059
- Report Number(s):
- BNL-222053-2021-JAAM
- Journal Information:
- ACS Catalysis, Vol. 11, Issue 15; ISSN 2155-5435
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Similar Records
Chemical Insights into the Formation of Colloidal Iridium Nanoparticles from In Situ X-ray Total Scattering: Influence of Precursors and Cations on the Reaction Pathway
A highly active and stable IrO x /SrIrO 3 catalyst for the oxygen evolution reaction