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Demetra Achilleos1 Hatice Kasap1 Erwin Reisner1

1, Christian Doppler Laboratory for Sustainable SynGas Chemistry, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK., University of Cambridge, Cambridge, , United Kingdom

The accelerated consumption of fossil fuels and the emerging ecological concerns, due to the alarming concomitant rise in greenhouse gas emissions, emphasize the need for the society to move towards renewable “green” resources. Photocatalysis is a promising approach for mitigating simultaneously both the energy and environmental concerns, since it allows the storage of the abundant solar energy in high energy density fuels, such as H2 (120 MJ/kg),1 in benign aqueous media. However, the development of economically sustainable processes for this purpose, creates the pressing need for new photosensitizers and catalysts of low cost and toxicity, which however maintain substantial performances.
Carbon dots (CDs) can efficiently serve as photoabsorbers for this purpose since they fulfil all these requirements.2-5 In particular, CDs are hydrophilic nanoparticles of low toxicity, which can be synthesized at low cost, are chemically and photochemically robust and show optimum photocatalytic properties upon pre-designed synthesis.6,7 In this work, we focus on the synthesis of CDs from naturally abundant and inexpensive biopolymers of various compositions and nanoarchitectures, which bestow the derived photoabsorbers with distinctive photocatalytic performances. These light harvesters when combined with noble-metal free molecular catalysts in aqueous-based photocatalytic systems, not only allow for substantial “green” fuel synthesis but also simultaneously facilitate waste oxidation. Such substrates which originate from numerous resources and are abundantly available at no cost, serve as electron donors to quench the photogenerated holes and maintain the photocatalytic stabilities of the systems. The use of waste materials for this purpose, eliminates the need for additional sacrificial reagents,8 traditionally used in great excess, which add to the overall cost of the processes, and often result in by-products which need to be disposed. We anticipate that this approach, could be a breakthrough in the development of scalable, economically and environmentally sustainable photocatalytic systems, which could efficiently serve the increased energy needs of our societies.
References
1. Kamat, P. V.; Bisquert, J. J. Phys. Chem. C 2013, 117, 14873.
2. Martindale, B. C. M.; Hutton, G. A. M.; Caputo, C. A.; Reisner, E. JACS 2015, 137, 6018.
3. Hutton, G. A. M.; Reuillard, B.; Martindale, B. C. M.; Caputo, C. A.; Lockwood, C. W. J.; Butt, J. N.; Reisner, E. JACS 2016, 138, 16722.
4. Hutton, G. A. M.; Martindale, B. C. M.; Reisner, E. Chem. Soc. Rev. 2017, 46, 6111.
5. Martindale, B. C. M.; Hutton, G. A. M.; Caputo, C. A.; Prantl, S.; Godin, R.; Durrant, J. R.; Reisner, E. Angew. Chem. Int. Ed. 2017, 56, 6459.
6. Yu, H.; Shi, R.; Zhao, Y.; Waterhouse, G. I. N.; Wu, L.-Z.; Tung, C.-H.; Zhang, T. Adv. Mater. 2016, 28, 9454.
7. Wang, R.; Lu, K.-Q.; Tang, Z.-R.; Xu, Y.-J. J. Mater. Chem. A 2017, 5, 3717.
8. Pellegrin, Y.; Odobel, F. C. R. Chim. 2017, 20, 283.

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