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Co oxide nanostructures for electrocatalytic water-oxidation: Effect of dimensionality and related properties

Abstract

A facile hydrothermal synthesis route was explored to obtain various nanostructures of Co oxide for applications in electrocatalytic water-splitting. The effect of reaction time and metal precursor ions on the morphology of synthesized nanostructures was studied in detail with the aid of scanning electron microscope. By systematic optimization of the synthesis parameters, Co oxide nanostructures with single dimensionality were obtained in the form of 0D nanoparticles (NPs), 1D nanowires (NWs), 2D nanosheets (NSs) and 3D nanocrystals (NCs). The effectiveness of the developed nanostructures towards oxygen evolution reaction (OER) was studied and promising OER activity was recorded for all the samples. Amongst all the developed catalysts, Co(OH)2 NPs showed the lowest overpotential of 339 mV to achieve current density of 10 mA/cm2, which is even lower than that of noble-metal oxides such as commercial RuO2 catalyst (370 mV). The specific effect of different parameters such as BET surface area, phase, crystallographic orientation of surface lattice planes, electroactive surface area and surface active species on the OER performance was studied. It was found that Co3O4 phase is more active for OER, compared to Co(OH)2 phase. However, Co(OH)2 NPs showed the best OER performance owing to their higher BET surface area, thereby underlining the significance of catalyst surface area. The effect of number of active surface atoms was demonstrated by estimating the electroactive surface area of all Co3O4 nanostructures. It was also shown that formation of CoO2 species (Co(IV)) on the surface is more beneficial for OER as compared to formation of CoOOH species (Co(III)). Finally, robustness of the developed Co3O4 nanostructures was established by performing recycling test for OER (1000 cycles) and the observed change in catalytic activity was correlated with morphological variation.

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Publication details

The article was received on 13 Jan 2018, accepted on 05 Apr 2018 and first published on 06 Apr 2018


Article type: Paper
DOI: 10.1039/C8NR00348C
Citation: Nanoscale, 2018, Accepted Manuscript
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    Co oxide nanostructures for electrocatalytic water-oxidation: Effect of dimensionality and related properties

    S. Gupta, A. Yadav, S. Bhartiya, M. Singh, A. Miotello, A. Sarkar and N. Patel, Nanoscale, 2018, Accepted Manuscript , DOI: 10.1039/C8NR00348C

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