A ³¹P NMR Investigation of the CoPi Water‐Oxidation Catalyst

Abstract

Beneath the sheets: (31) P NMR data suggests that phosphates are liberated freely in the interlayer of a cobalt-hydroxide water-oxidation catalyst. The cobalt-hydroxide sheets are separated by an interlayer region with water, counterions and phosphate, which help to shuttle protons as the layer develops charge.

First turnover analysis of water-oxidation catalyzed by Co-oxide nanoparticles

“…33,34 The presence of corner sharing complete and incomplete Co 4 O 4 cubanes was also discussed, but this appears to be a less common motif. 34,[36][37][38] Overall, the CoP i -oxide films appear to be similar in water-splitting activity to earlier studied CoO(OH) and Co 3 O 4 ; interestingly, all these Co-forms convert into each other over time depending on the applied potentials. P i ) and other counterions ( Figure 1A).…”

“…39,[46][47][48][49][50][51] Structural and elemental information on the Co/M2P-oxide NP is available from an EXAFS study, 52 from XRD and XPS (Text S1 and Figures S1-S3 †), light scattering 24 and electron microscopy experiments ( Figure 1D). 24 30,34,[36][37][38]52 Fig. 30,33 The role of M2P appears to be to limit the growth of the Co/M2P-oxide NP, since particles up to 2500 nm were obtained in presence of only P i instead of M2P and P i .…”

“…52 Importantly, 31 P NMR measurements on CoP i -oxides suspensions showed that P i is mobile within CoP i -oxides. 37 It is thus an open question if in aqueous suspensions M2P is a terminal ligand to Co or not. In the resting state, which the CoP i -oxides attain a few minutes after catalysis, the Co atoms are predominantly in the oxidation state Co III , 30,35,53,54 but also some Co II and Co IV ions were detected by EPR spectroscopy.…”

Water Oxidation by Co‐Based Oxides with Molecular Properties

“…The location of phosphate anions cannot be deduced conclusively by EXAFS or PDF analysis [58]; terminal phosphate coordination do not contradict the results. However, recent nuclear magnetic resonance (NMR) measurements support the presence of phosphate anions between CoCat clusters [84], while excluding phosphate groups bound to Co hydroxide. As discussed earlier, the nonbinding monovalent cations are most likely also located between Co-oxo clusters, which is further supported by the facile exchange of the redox-inert cations [34].…”

A Fundamental Investigation on the Structural Dynamics of Model Siloxane Networks under Extreme Pressure

“…[3][4][5][6][7][8][9] Incorporation of high pressure probes to these spectroscopies has already been established in the solution state by the PI. [10][11][12][13] In addition, a preliminary experiment on an model PDMS network did yield a sudden change in relaxation that could indicate a phase transition, see Fig. 2.…”