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Influence of Carbonaceous Species on Aqueous Photo-catalytic Nitrogen Fixation by Titania

Abstract

For decades, reports have suggested that photo-catalytic nitrogen fixation by titania in an aqueous environment is possible. Yet consensus does not exist regarding how the reaction proceeds. Furthermore, the presence of an aqueous protonated solvent and the similarity between the redox potential for nitrogen and proton reduction suggest that ammonia production is unlikely. Here, we re-investigate photo-catalytic nitrogen fixation by titania in an aqueous environment through a series of photo-catalytic and electrocatalytic experiments. Photo-catalytic testing reveals that mineral phase and metal dopants play a marginal role in promoting nitrogen photofixation, with ammonia production increasing when the majority phase is rutile and with iron dopants. However, the presence of trace amount of adsorbed carbonaceous species increased the rate of ammonium production by two times that observed without adsorbed carbon based species. This suggests that carbon species play a potential larger role in promoting the nitrogen fixation process over mineral phase and metal dopants. We also demonstrate an experimental approach aimed to detect low-level ammonium production from photo-catalyst using rotating ring disk electrode experiments conducted with and without illumination. Consistent with the photocatalysis, the ammonia oxidation peak is discernible with the rutile phase titania, but is not present with the mix-phased titania. Rotating ring disk electrode experiments may also provide a new avenue to attain a higher degree of precision in detecting ammonia at low levels.

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Publication details

The article was received on 19 Nov 2018, accepted on 05 Feb 2019 and first published on 08 Feb 2019


Article type: Paper
DOI: 10.1039/C8FD00191J
Citation: Faraday Discuss., 2019, Accepted Manuscript

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    Influence of Carbonaceous Species on Aqueous Photo-catalytic Nitrogen Fixation by Titania

    Y. Liu, M. Vu, J. Lim, T. Do and M. C. Hatzell, Faraday Discuss., 2019, Accepted Manuscript , DOI: 10.1039/C8FD00191J

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