Hydrolytically Stable Phosphorylated Hybrid Silicas for Proton Conduction

Authors

  • Y. G. Jin,

    1. ARC Centre of Excellence for Functional Nanomaterials, Australian Institute of Bioengineering and Nanotechology, The University of Queensland, QLD 4072 (Australia)
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  • S. Z. Qiao,

    1. ARC Centre of Excellence for Functional Nanomaterials, Australian Institute of Bioengineering and Nanotechology, The University of Queensland, QLD 4072 (Australia)
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  • J. C. D. da Costa,

    1. ARC Centre of Excellence for Functional Nanomaterials, Australian Institute of Bioengineering and Nanotechology, The University of Queensland, QLD 4072 (Australia)
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  • B. J. Wood,

    1. Brisbane Surface Analysis Facility, The University of Queensland, QLD 4072 (Australia)
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  • B. P. Ladewig,

    1. ARC Centre of Excellence for Functional Nanomaterials, Australian Institute of Bioengineering and Nanotechology, The University of Queensland, QLD 4072 (Australia)
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  • G. Q. Lu

    1. ARC Centre of Excellence for Functional Nanomaterials, Australian Institute of Bioengineering and Nanotechology, The University of Queensland, QLD 4072 (Australia)
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  • The authors acknowledge the financial support for this project from the Australian Research Council and the ARC Federation Fellowship (to Prof. G. Q. Lu).

Abstract

A new approach to the synthesis of fully immobilized phosphorus functionalized hybrid proton conductive gels based on phosphonic acid grafting is presented in this paper. The hybrid silicas with different amounts of phosphonic acid have been prepared and characterized using Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller surface area analysis, thermogravimetric analysis, and electrochemical techniques. The proton conductivity of the materials depend strongly on hydration, which increases by four orders of magnitude over the relative humidity (RH) range of 20 to 100 %, up to a maximum of 0.027 S cm–1 at 100  °C and 100 % RH. For the reported samples, proton conduction is believed to occur within a dynamic hydrogen-bond network formed by functionalized P–OH groups and water molecules by the Grotthuss mechanism. However, the proton conductive sites (P–OH) are likely to be partially immobilized by strong protonic receptors (N atoms in amines), which reduces the free P–OH groups and restricts proton transfer. Hydration may cause a bonding structural rearrangement, which results in more free P–OH groups as active proton conductive sites and, therefore, greatly increased proton conductivity is observed.

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