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Calcium containing iron oxide as an efficient and robust catalyst in (photo-)electrocatalytic water oxidation at neutral pH

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Abstract

We report on calcium containing iron oxide thin films (CaFeOx), prepared by spin-coating and a follow-up annealing process under mild condition, as an efficient and robust catalyst in electrocatalytic and photoelectrocatalytic water oxidation at neutral pH. Thin films prepared without calcium are essentially crystalline γ-Fe2O3, but those prepared with calcium are amorphous, and with optimal calcium content, the resultant film consists of a short-range order γ-Fe2O3 domain embedded in an amorphous Ca2Fe2O5 matrix. CaFeOx prepared with optimal calcium content decomposes upon exposure to phosphate, resulting in the leaching of surface calcium and formation of redox-active iron phosphate, which prevents the loss of active iron species from etching by protons released from the water oxidation process. The amorphous nature and in situ formation of iron phosphate render CaFeOx with high activity and stability under high turnover conditions, reaching 10 mA cm−2 at an overpotential (η) of ∼650 mV with a small increase in η (∼30 mV) over 2 h electrolysis in phosphate buffer (1.0 M, pH 7). When being integrated onto a BiVO4 photoanode, CaFeOx greatly improves the kinetics of the OER and interfacial hole transfer at BiVO4, resulting in remarkable enhancement in its photocurrent response and photostability.

Graphical abstract: Calcium containing iron oxide as an efficient and robust catalyst in (photo-)electrocatalytic water oxidation at neutral pH

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Publication details

The article was received on 13 Sep 2017, accepted on 02 Nov 2017 and first published on 02 Nov 2017


Article type: Paper
DOI: 10.1039/C7SE00447H
Citation: Sustainable Energy Fuels, 2018, Advance Article
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    Calcium containing iron oxide as an efficient and robust catalyst in (photo-)electrocatalytic water oxidation at neutral pH

    H. Chiu, W. Huang, L. Hsu, Y. Lin, Y. Lai and C. Lin, Sustainable Energy Fuels, 2018, Advance Article , DOI: 10.1039/C7SE00447H

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