Mechanistic Investigation into Efficient Water Oxidation by Co-Ni-Based Hybrid Oxide-Hydroxide Flowers

Devi, HR and Nandan, R and Nanda, KK (2020) Mechanistic Investigation into Efficient Water Oxidation by Co-Ni-Based Hybrid Oxide-Hydroxide Flowers. In: ACS Applied Materials and Interfaces, 12 (12). pp. 13888-13895.

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Abstract

Oxides are envisioned as promising catalysts to facilitate water oxidation, and the benign presence of hydroxide moieties can further enhance the catalyst performance. However, the nature of synergy between oxides and hydroxides remains elusive. In this study, we have designed a one-pot solution growth technique for the synthesis of flower-shaped N-doped-C-enveloped NiCo2O4/NixCo(1-x)(OH)y catalysts with varying oxide and hydroxide contents and investigated their water oxidation behavior. The correlation between performance-determining parameters involved in water oxidation, such as the onset potential and overpotential with oxide and/or hydroxide content, oxidation states (oxides), and elemental composition (Co/Ni content), and the possible ways to achieve their optimal values are discussed in detail. Our observations conclude that the onset potential and overpotential are minimal for the hybrid oxide-hydroxide bimetallic system compared with pristine hydroxide or oxide. The optimal hybrid catalyst shows excellent current density, low Tafel slope (82 mV/dec), and low onset potential (281 mV at 2 mA/cm2) and overpotential (348 mV at 10 mA/cm2), besides enduring operational stability in alkaline medium. The low Tafel slope suggests the preferable kinetics for water oxidation, and the poisoning study reveals the direct involvement of metal as active sites. The overall study unveils the synergy in the Co-Ni-based binary transition-metal oxide-hydroxide hybrid, which makes it a potential candidate for water oxidation catalysts, and hence, it is expected that the hybrid will find applications in energy conversion devices, such as electrolyzers

Item Type:	Journal Article
Publication:	ACS Applied Materials and Interfaces
Publisher:	American Chemical Society
Additional Information:	The copyright for this article belongs to the American Chemical Society
Keywords:	Doping (additives); Electrocatalysts; Energy conversion; Nickel oxide; Oxidation; Slope stability; Transition metal oxides; Transition metals, bimetallic; Elemental compositions; Energy conversion devices; hybrid oxide-hydroxide flowers; poison; Solution growth technique; Water oxidation; Water oxidation catalysts, Cobalt compounds
Department/Centre:	Division of Chemical Sciences > Materials Research Centre
Date Deposited:	01 Feb 2023 09:29
Last Modified:	01 Feb 2023 09:29
URI:	https://eprints.iisc.ac.in/id/eprint/79682

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