Nanocarbon-inorganic hybrid materials for photocatalytic applications
Final Report Abstract
Nanocarbon-inorganic hybrids are a new class of functional materials with the potential to advance their application in socioeconomically important fields related to sustainable energy and environment. These include batteries, sensors, photovoltaics and different types of catalysis. Photocatalysis is a particularly promising application, as it harnesses sunlight for the conversion of abundant materials, such as water and CO2, into useful chemicals and fuels, such as hydrogen, through green chemistry. Inefficient charge separation and extraction often limits the performance of these applications. The purposeful combination of complementary functional compounds into hybrid structures can facilitate these processes through interfacial charge and energy transfer and thus can provide a promising solution. In this project, we hybridized various types of nanocarbons, including carbon nanotubes, graphene and aerographite, as excellent charge collectors and conductors, with inorganic metal oxides as semiconducting light absorbers and efficient photocatalysts. We developed a synthesis process that utilizes aromatic linker molecules for the deposition of thin layers and nanoparticles with atomic preciseness on the nanocarbon’s surface without disrupting their structure and properties. Based on this process, we developed a new hybrid based on thin layers of single-crystalline Ta2O5, which yielded some of the to-date highest activities for photocatalytic hydrogen evolution via sacrificial water splitting. As another highlight, we were able to experimentally proof the existence of interfacial charge transfer in these hybrids. First, we developed a new photospectroscopic technique that separates the transfer of photoexcited charge carriers from co-existing intrinsic photocurrent effects. Second, we designed a unique hybrid sandwich structure by adding dielectric barrier layers between the nanocarbon and ZnO and measured the fluorescence quenching behaviour as a function of barrier thickness. This way, we demonstrated that the extent of charge transfer can be tuned by varying the type and crystallinity of the barrier layer as well as though engineering the electrochemical potential (i.e. Fermi level) of the nanocarbons. Another important question in the community involves the nature of active sites in nanocarbon hybrid photocatalysts. We could answer this question with our hybrid sandwich structures and proofed that the performance of photocatalysts is limited by the access of reactants to the socalled triple phase boundaries, i.e. the interface between the nanocarbon, the inorganic compound and the liquid reaction media. This project yielded some of the currently most active photocatalysts for hydrogen evolution and other important reactions connected with solar fuels. It also produced intriguing and unexpected results that have increased our fundamental knowledge on the working principles of nanocarbons hybrids. This project will thus pave the way for future advancements in photocatalysis and other applications concerning sustainable energy and the environment.
Publications
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“Application of Functional Hybrids Incorporating Carbon Nanotubes or Graphene”, in “Carbon Nanotubes and Graphene”, Elsevier, 2014
C. J. Shearer, A. S. Cherevan, D. Eder
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Non-destructive functionalisation for atomic layer deposition of metal oxides on carbon nanotubes: effect of linking agents and defects Nanoscale, 7, 3028-3034 (2015)
N. Kemnade, C. J. Shearer, D. J. Dieterle, A. S. Cherevan, P. Gebhardt, G. Wilde and D. Eder
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Oxygen vacancies and interfaces enhancing photocatalytic hydrogen production in mesoporous CNT/TiO2 hybrids, Applied Catalysis B: Environmental, 179, 574-582, (2015)
A. Moya, A. Cherevan, S. Marchesan, P. Gebhardt, M. Prato, D. Eder, J. J. Vilatela
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Dual excitation transient photocurrent measurement for charge transfer studies in nanocarbon hybrids and composites Adv. Mater. Interfaces, 3, 1600244 (2016)
A. S. Cherevan, D. Eder
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“Nanocarbon Hybrid Materials”, in “Carbon Nanomaterials Sourcebook”, CRC Press, 2016
A. S. Cherevan, P. Gebhardt, C. Shearer, D. Eder
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Beware of Doping: Ta2O5 Nanotube Photocatalyst Using CNTs as Hard Templates. ACS Applied Energy Materials, 2018, 1 (3), 1259-1267
A. Cherevan, P. Gebhardt, A. Kunzmann, R. D. Costa and D. Eder
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Comparison of Doping Levels of Single ‑Walled Carbon Nanotubes Synthesized by Arc‑ Discharge and Chemical Vapor Deposition Methods by Encapsulated Silver Chloride Phys. Status Solidi B, 2018, 255: 1800178
M. V. Kharlamova, C. Kramberger, O. Domanov, A. Mittelberger, T. Saito, K. Yanagi, T. Pichler, D. Eder
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Fermi level engineering of metallicity-sorted metallic single-walled carbon nanotubes by encapsulation of few-atom-thick crystals of silver chloride Journal of Materials Science, 2018, 53 (18), 13018–13029
M. V. Kharlamova, C. Kramberger, O. Domanov, A. Mittelberger, K. Yanagi, T. Pichler, D. Eder
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How to Evaluate and Manipulate Charge Transfer and Photocatalytic Response at Hybrid Nanocarbon–Metal Oxide Interfaces Advanced Functional Materials, 2018, 28, 1704730
N. Kemnade, P. Gebhardt, G. M. Haselmann, A. S. Cherevan, G. Wilde and D. Eder
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Silver Chloride Encapsulation-Induced Modifications of Raman Modes of Metallicity- Sorted Semiconducting Single-Walled Carbon Nanotubes Journal of Spectroscopy, Vol. 2018, Article ID 5987428
M. V. Kharlamova, C Kramberger, A Mittelberger, K Yanagi, T Pichler, D Eder
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Characterization of the Electronic Properties of Single-Walled Carbon Nanotubes Filled with an Electron Donor–Rubidium Iodide: Multifrequency Raman and X-ray Photoelectron Spectroscopy Studies Phys. Status Solidi B, 2019: 1900209
M. V. Kharlamova, C. Kramberger, P. Rudatis, K. Yanagi, D. Eder
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Revealing the doping effect of encapsulated lead halogenides on single‑walled carbon nanotubes Applied Physics A, 2019, 125: 320
M. V. Kharlamova, C. Kramberger, P. Rudatis, T. Pichler, D. Eder
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“Synthesis and Properties of Single-Walled Carbon Nanotubes Filled with Metal Halogenides and Metallocenes”, in “Perspective of Carbon Nanotubes”, IntechOpen, 2019
M. V. Kharlamova, D. Eder
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“Carbon nanotubes: synthesis, properties and new developments in research”, in “Nanocarbons and their hybrids: from synthesis to applications”, Wiley
M. V. Kharlamova, D. Eder
