Cobalt-to-vanadium charge transfer in polyoxometalate water oxidation catalysts revealed by 2p3d resonant inelastic X-ray scattering

Abstract

Two isostructural cobalt containing polyoxometalate water oxidation catalysts, [Co(HO)(α-PWO)] (Co4P2) and [Co(HO)(α-VWO)] (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.

Saturation and self-absorption effects in the angle-dependent 2p3d resonant inelastic X-ray scattering spectra of Co3+

“…out ) implies that the partial fluorescence yield X-ray absorption is not identical to the normal absorption. Liu et al show good agreement of such state-dependent behavior between experimental and calculated results in dilute specimens (Liu et al, 2018). If S Co (!…”

Polyoxometalates: Tailoring metal oxides in molecular dimension toward energy applications

“…By leveraging the electrochromic properties of Well-Dawson-type polyoxometalates based on K 10 231 The electrochromic properties are available in K 6 P 2 W 18 O 62 when it is combined with TiO 2 nanowires, resulting in excellent switching and transmittance properties. 232 Polyoxotungstates have been employed in a number of energy conversion and storage applications 36,43,228,[233][234][235][236][237][238][239][240][241][242] and sensors. 145,[243][244][245][246][247] 6 | POLYOXOMOLYBDATE Molybdenum trioxide with the formula MoO 3 has been applied as catalysts and synthesizing agent, and its polyoxometalate counterpart polyoxomolybdate has been widely studied to modulate their electronic and optoelectronic properties for energy conversion and storage applications.…”

“…The electrochromic properties are available in K 6 P 2 W 18 O 62 when it is combined with TiO 2 nanowires, resulting in excellent switching and transmittance properties . Polyoxotungstates have been employed in a number of energy conversion and storage applications and sensors …”

Tailored Assembly of Molecular Water Oxidation Catalysts on Photoelectrodes for Artificial Photosynthesis

“…For example, it is well‐known that electrocatalytic activity of organometallic compounds can be finely tuned by varying types of central metal ions and controlling the surrounding environments of metal ions with ligand molecules (Figureàa–b) , . Another well‐known example includes polyoxometalate‐based molecular electrocatalysts; due to their all‐inorganic and fully oxidized nature, they can readily and stably accommodate high oxidation state metal‐oxo clusters, beneficial for multielectron redox reactions such as water oxidation . Moreover, they exhibit rich electrochemistry through control over metal‐oxo clusters, partial substitution of oxide‐forming metal elements, and the degree of their condensation (Figure c‐d) , .…”