Abstract
Two isostructural cobalt containing polyoxometalate water oxidation catalysts, [Co4(H2O)2(α-PW9O34)2]10- (Co4P2) and [Co4(H2O)2(α-VW9O34)2]10- (Co4V2), exhibit large differences in their catalytic performance. The substitution of phosphorus centers in Co4P2 with redox-active vanadium centers in Co4V2 leads to electronic structure modifications. Evidence for the significance of the vanadium centers to catalysis, predicted by theory, was found from soft X-ray absorption (XAS) and resonant inelastic X-ray scattering (RIXS). The XAS and RIXS spectra determine the electronic structure of the cobalt and vanadium sites in the pre-reaction state of both Co4V2 and Co4P2. High-energy resolution RIXS results reveal that Co4V2 possesses a smaller ligand field within the tetra-cobalt core and a cobalt-to-vanadium charge transfer band. The differences in electronic structures offer insights into the enhanced catalysis of Co4V2.
| Original language | English |
|---|---|
| Pages (from-to) | 4554-4562 |
| Number of pages | 9 |
| Journal | Physical Chemistry Chemical Physics |
| Volume | 20 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - 1 Jan 2018 |
Funding
This work is financially supported by the China Scholarship Council (CSC) and the ERC advanced grant XRAYonACTIVE, number 340279. CLH thanks the DOE, Office of Basic Science, Solar Photochemistry program (grant DE-FG02-07ER15906) for support. The synchrotron radiation experiments at the HORNET end station of BL07LSU of SPring-8 were carried out by the joint research in the Synchrotron Radiation Research Organization and the Institute for Solid State Physics, the University of Tokyo (Proposal No. 2013B7458, 2014A7470). We are grateful to ANKA and to the Karlsruhe Nano Micro Facility (KNMF) for the provision of beamtime. We thank the onsite assistances by Meng-jie Huang, Peter Nagel, and Michael Merz in ANKA, Dr Jun Okamoto in NSRRC and Dr Jun Miyawaki in SPring-8.