DOI: 10.25903/5e2505b26b219
title: The role of structural disorder in increasing the activity of cobalt oxide and manganese oxide water oxidation catalysts

description: <p>This dataset consists of 36 spreadsheets containing raw data and charts for the figures included in the research chapters of the author's thesis.</p>
<p>Chapter 2 of the thesis examines disorder in heterogenite-like cobalt oxides. It presents a structure versus function study for a series of phosphate doped heterogenite-like cobalt oxides with the aim of explaining the mechanistic importance of disorder in Kanan and Nocera’s highly efficient 'Co-Pi'(heterogenite-like cobalt oxide with phosphate) electrocatalyst. The phosphate doped heterogenite-like cobalt oxide series was synthesised ex situ to allow an in-depth structural characterisation of the materials by X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM). The relationship between thermodynamic stability and catalytic activity was examined by measuring the oxidative strength of each material in a reaction with hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>).  </p>
<p>Chapter 3 examines disorder in birnessite-like manganese oxides. It presents a structure versus function study for disordered and ordered birnessite-like manganese (III,IV) oxides with the aim of explaining why disordered birnessite phases are more catalytically active than ordered birnessite phases. The two disordered birnessite-like phases (one with 2D stacking disorder and one with no crystalline order) and an ordered birnessite-like phase were comprehensively structurally characterised by X-ray diffraction (XRD), XAS and TEM. The thermodynamic stability of each material was quantified by examining how each material functioned in the competitive 'direct oxidation' / 'catalytic disproportionation' reaction with H<sub>2</sub>O<sub>2</sub>. </p>
<p>Chapter 4 examines heterogenite-like cobalt oxides in an in situ XAS-electrochemical study. It presents the design and utilisation of a new spectroelectrochemical cell for the investigation of electrochemical and photoelectrochemical reaction mechanisms during in situ XAS-electrochemical experiments. Specifically, the cell was used to study the reaction mechanisms of two heterogenite-like cobalt oxides and to quantify X-ray beam-induced phenomenon associated with the in situ characterisation of these samples. </p>
<p>The relevant figures/files are listed below and in the thesis:</p>
<ul>
<li>Figure 2.1: Powder XRD spectra collected on bulk heterogenite, CoO<sub>x</sub> (0 %P), and CoO<sub>x</sub> (9 %P)</li>
<li>Figure 2.2: XRD simulations of single crystal heterogenite</li>
<li>Figure 2.4 a, b: Co K-edge XAS spectra collected on the CoOx (x %P) series in transmission mode</li>
<li>Figure 2.10: FTIR data collected on the CoO<sub>x</sub> (x %P) series</li>
<li>Figure 2.15: Cyclic voltammetry of the CoO<sub>x</sub> (x %P) series (analysed in 0.1 M, pH 7 phosphate buffer)</li>
<li>Figure 2.17: Cyclic voltammetry analysis of CoO<sub>x</sub> (0 %P) (analysed in 0.1 M, pH 7 phosphate buffer) for 50 cycles</li>
<li>Figure 2.18: Tafel plot containing the Tafel slopes for the CoO<sub>x</sub> (x %P) series and bulk heterogenite</li>
<li>Figure 2.19: Ex situ measure of water oxidation catalysis using hypochlorite as a sacrificial oxidant. Gas evolution is presented as a total after 5 mins of reaction</li>
</ul>
<ul>
<li>Figure 3.5: Mn K-edge XAS data collected on the manganese oxide samples</li>
<li>Figure 3.6: Visual representation of the EXAFS fits for the manganese oxides</li>
<li>Figure 3.7: Oxidation state calculation for the manganese oxide materials</li>
<li>Figure 3.9: XRD spectra for the manganese oxides and a biogenic manganese</li>
<li>oxide sample</li>
<li>Figure 3.13: Activity of the manganese oxide samples for the ex situ water</li>
<li>oxidation reaction using Ce<sup>IV</sup> as a chemical oxidant</li>
<li>Figure 3.14: Mn K-edge XAS data of screen-printed 0%Pi-MnOx</li>
<li>Figure 3.16: CV data collected on the manganese oxide samples</li>
<li>Figure 3.21 a, b: Ce L1-edge data collected on Ce<sup>3+</sup> and Ce<sup>4+</sup> in the Mn K-edge region</li>
<li>Figure 3.22: Mn K–edge XANES spectra collected on samples manganese oxide with Ce<sup>IV</sup> samples</li>
</ul>
<ul>
<li>Figure 4.3: Cyclic voltammetry (v = 0.020 V s<sup>-1</sup>; quasi-stabilized fifth cycle shown) of a nickel (Ni0)-modified gold electrode in contact with an Ar-saturated 0.1 M NaOH</li>
<li>Figure 4.4: Cyclic voltammetry of each CoO<sub>x</sub>  and CoO<sub>x</sub> NTA modified electrode</li>
<li>Figure 4.5: Single Co K-edge X-ray absorption spectra collected in situ for cobalt oxides on 1 mm thick glassy carbon and CoOxNTA on 0.5 mm thick ITO/PET</li>
<li>Figure 4.6: Electrochemical and spectroscopic data collected on nickel-based materials</li>
<li>Figure 4.7 a, b, c, d: Electrochemical and in situ Co K-edge XAS data collected on CoO<sub>x</sub> /ITO/PET and CoO<sub>x</sub> NTA/ITO/PET</li>
<li>Figure 4.8: Chronoamperomograms recorded on CoO<sub>x</sub> /ITO/PET and CoOxNTA/ITO/PET during spectroscopic data collection</li>
<li>Figure 4.9: In situ Co K-edge XANES data collected on a very low loading of CoO<sub>x</sub> <sup>NTA</sup>. CoO<sub>x</sub> <sup>NTA</sup> (Γ = 0.4 mC cm<sup>-2</sup> ≈ 4 nmol cm<sup><span style="font-size: 9.16667px;">-2</span></sup>) was electrodeposited onto ITO/PET in contact with 0.1 M borate buffer (pH 9.2)</li>
</ul>
<p> </p>