A homogeneous solution of Co(ii) in acetate buffer at pH 7 is found to be an efficient water oxidation catalyst (WOC) showing significantly greater current density than Co(ii) in phosphate buffer (Co-Pi) under identical conditions owing to the higher solubility of the former. When electrodeposited on ITO/FTO electrodes it forms acetate bound cobalt(ii)-oxide materials (Co-Ac-WOC) showing a catalytic current density of 0.1 mA cm-2 at 830 mV and 1 mA cm-2 at 1 V in a pH 7 buffer solution. The morphology of Co-Ac-WOC and its evolution with time and deposition potential is investigated with AFM, HR-TEM and SEM. The chemical composition of Co-Ac-WOC is investigated using XPS, EDX, ATR-FTIR and combustion analysis which indicate that this material has a CoO core with chloride and acetate anions bound to the Co center. Sodium is found to be integrated in the Co-Ac-WOC. The presence of the sodium and chloride ions lowers the onset potential for the oxygen evolution reaction (OER) by 240 mV relative to the classic Co-Pi at pH 7. The lower onset potential and higher OER current lowers the exchange current density to 10-6.7 A cm-2 in Co-Ac-WOC relative to 10-8-10-10 A cm-2 in Co-Pi and its derivatives.
ASJC Scopus subject areas
- Physics and Astronomy (all)
- Physical and Theoretical Chemistry