A Benchmark Quantum Yield for Water Photoreduction on Amorphous Carbon Nitride

Mohammad Rahman, Patrick Tapping, Tak Kee, Ronald Smernik, Nigel Spooner, Jillian Moffatt, Youhong Tang, Kenneth Davey, Shi-Zhang Qiao

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    Amorphous carbon nitride (a-CN) is a less-explored but promising photocatalyst for hydrogen production. Despite an extended visible light absorption (EVLA) its low quantum efficiency (QE) for water photoreduction is a long standing problem. This implies that EVLA is not proportionally translated into collection of large amounts of photogenerated electrons. Minimizing the mismatch between light-absorption and charge-collection remains a scientific challenge. Here a sponge-like hierarchical structure of a-CN that addresses this apparent mismatch is reported. Combined experimental and finite difference time domain simulations demonstrate the ability of the a-CN sponge to induce scattering for total internal light reflection that promotes localized charge carrier generation. Diffused reflectance and transient fluorescence decay studies show good agreement with simulations with a 40% enhanced light-trapping and an ≈23 times longer electron lifetime in spongy a-CN compared with that of the bulk material. The result is a new high benchmark for hydrogen production of 203.5 µmol h−1 with a QE of 6.1% at 420 nm in a reaction system of 10 vol% triethanolamine and 1 wt% Pt cocatalyst. The enhanced water photoreduction is a result of amenable photophysical and electrochemical attributes existing within the a-CN sponge.

    Original languageEnglish
    Article number1702384
    Pages (from-to)Art: 1702384
    Number of pages11
    JournalAdvanced Functional Materials
    Issue number39
    Publication statusE-pub ahead of print - 2017

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    Rahman, M., Tapping, P., Kee, T., Smernik, R., Spooner, N., Moffatt, J., Tang, Y., Davey, K., & Qiao, S-Z. (2017). A Benchmark Quantum Yield for Water Photoreduction on Amorphous Carbon Nitride. Advanced Functional Materials, 27(39), Art: 1702384. [1702384]. https://doi.org/10.1002/adfm.201702384