The use of hot electrons generated from the decay of surface plasmons is a novel concept that promises to increase the conversion yield in solar energy technologies. Titanium nitride (TiN) is an emerging plasmonic material that offers compatibility with CMOS technology, corrosion resistance, as well as mechanical strength and durability, thus outperforming noble metals in terms of cost, mechanical, chemical and thermal stability…
Nanoporous Nitrogen-Doped Graphene Oxide/Nickel Sulfide Composite Sheets Derived from a Metal-Organic Framework as Efficient Electrocatalyst for Hydrogen and Oxygen Evolution
We report the rational design and in situ synthesis of hierarchical porous nanocomposite sheets of nitrogen-doped graphene oxide (NGO) and nickel sulfide (Ni7S6) derived from a hybrid of a well-known nickel-based metal-organic framework (NiMOF-74) using thiourea as a sulfur source. The nanoporous NGO/MOF composite was prepared through a solvothermal process in which Ni(II) metal centers of the MOF structure were chelated with nitrogen and oxygen functional groups of NGO. NGO/Ni7S6 exhibits bifunctional activity…
Chemistry is fundamental for powering our society and plasmonics may have a transformative impact on the way we will drive, manipulate, enhance, and monitor chemical processes in the future. In our recent Perspective published in Science in collaboration with pioneers in the field of plasmonics such as Prof. Shalaev (Purdue University) and Prof. Brongersma (Stanford University), we discuss how hot-carrier driven transformations on metal surfaces offer the opportunity for exploring new types of chemistry that are typically only possible at high temperatures and pressures…
We have explored the morphological control effect of hierarchical heterostructure α-Fe2O3/TiO2 nanotube electrode by synthesizing varying morphologies of hierarchical heterostructure α-Fe2O3/TiO2 nanotube electrodes. Both the experimental results and theoretical analysis proved that ultrathin α-Fe2O3 nanoflakes branched on TiO2 nanotube electrode showed superior photocurrent density than other shaped α-Fe2O3 nanorod branched on TiO2 nanotube electrodes by balanced electrode design in both morphology and composition…
On the improvement of PEC activity of hematite thin films deposited by high-power pulsed magnetron sputtering method
We have effectively combined the high impulse magnetron sputtering (HiPIMS) synthetic approach with another powerful deposition method of atomic layer deposition (ALD) to fabricate highly active photoanodes based on very thin hematite films (~ 50 nm) deposited by HiPIMS and alumina (Al2O3) ultra-thin films coated over the hematite by ALD. In this way the backward recombination of photogenerated electrons and holes was highly reduced due to the passivation of undesirable surface states acting as traps…
Photoanodes with fully controllable texture: the enhanced water splitting efficiency of thin hematite films exhibiting solely (110) crystal orientation
Despite of computing models suggesting that the electrical conductivity of hematite is extremely anisotropic, revealing up to four orders of magnitude higher electron transport with conduction along the (110) hematite crystal plane, synthetic approaches allowing the sole growth in that direction have not been reported yet…
One-Dimensional Titanium Dioxide Nanomaterials: Nanotubes / Aligned metal oxide nanotube arrays: key-aspects of anodic TiO2 nanotube formation and properties
Over the past ten years, highly-defined layers of TiO2 nanotubes and aligned nanoporous arrays have attracted tremendous scientific and technological interest due to their impact on energy conversion, environment remediation and biocompatibility. In the two recently published review papers (Chemical Reviews 2014, and Nanoscale Horizons 2016), we try to give an overview on the state of the art of research on TiO2 nanotubes, their formation, properties, and applications…
Photoanodes based on TiO2 and α-Fe2O3 for solar water splitting – superior role of 1D nanoarchitectures and of combined heterostructures
Decades of experimental research on TiO2 (titania) and α-Fe2O3 (hematite) have pointed out that these two semiconductors are promising candidates as anodes for photoelectrochemical water splitting, mainly owing to their stability in a wide range of (photo-/electro)chemical conditions, their natural abundance and non-toxicity, and a low production cost. In spite of these remarkable aspects, limited charge transfer kinetics (intrinsic of both oxides) still hampers the development of efficient TiO2– and α-Fe2O3-based PEC devices that could fulfill the requirements for large-scale applications…
Scientific News In Photoelectrochemistry
Broadband hot electron collection for solar water splitting with plasmonic titanium nitride >>
Nanoporous Nitrogen-Doped Graphene Oxide/Nickel Sulfide Composite Sheets Derived from a Metal-Organic Framework as Efficient Electrocatalyst for Hydrogen and Oxygen Evolution >>
Head of the Division:
Brief research summary:
The Photoelectrochemical group aims at developing a new class of multicomponent hybrid systems (HNS) composed of a central material (CS), most likely metal oxides semiconductors (TiO2, α-Fe2O3, ZnO, WO3, BiVO4, etc.) and carbon based materials with controlled shape and dimensionality (e.g., 1D-nanotubes, 2D-ultrathin films, 3D branched nanoarchitectures, etc.) that will work as highly photocatalytically and electrocatalytically active materials for a broad portfolio of energy and environmental applications including direct splitting of water, photocatalysis, electrocatalysis, dye sensitized solar cells, etc.. The key-approach is represented by the simultaneous and synergistic combination of strategies (nanostructuring, co-catalyst deposition, surface sensitization) that are still very often studied and developed independently. Therefore, the nanostructured CMs are coupled to counterparts with specific functionalities (extended visible light absorption, remarkable efficiency in charge transfer, enhanced carrier mobility) and the effective interaction of the single components will significantly benefit the PEC efficiency of the composite system. The group is very well equipped for a thorough electrochemical, photoelectrochemical, and photocatalytic investigation of the materials and hybrid nanostructures developed.
Bullet specifications of the research activities:
Synthesis of central semiconductor (CS) photo-electrodes
- Low temperature pulse-modulated magnetron sputtering of nanocystalline 2D thin films; their nano-faceting and nano-gradients engineering for the formation of internal junctions; their elemental doping.
- Preparation of highly ordered and self-organized 1D nanotube (NT) arrays, by the electrochemical anodization of sputtered metal and metal alloy films
- Preparation of nanorod (NR) arrays by hydrothermal synthetic pathways.
- Advanced thermo-chemical treatment of these nanostructures (e.g., high pressure hydrogenation and nitridation
Modification of the CMs to address the major drawbacks limiting their catalytic performances
- Improvement of the charge dynamics: formation of metastable oxides (g., Fe2TiO5); synthesis and anchoring of graphene derivatives; deposition of multi-layered thin metal oxides to promote charge cascade (TiO2/Fe2O3, TiO2/WO3); formation of a tunnel barrier for preferential e– or h+ transport; anchoring of advanced co-catalysts with core-shell nanostructures and of MOFs.
- Sensitization of wide band gap MSs: attachment of tailored carbon quantum dots, plasmonic nanoparticles, inorganic and organic sensitizers, narrower band gap semiconductors, etc.
Advanced physical and PEC characterizations of the most promising HNS
- Advanced chemical, structural, and morphological characterization of photoanodes.
- PEC investigations (photocurrents, OCP, transient spectroscopy, OER, HER, etc.), impedance spectroscopy, solar water splitting performance.
- Theoretical description and models of HNS.
Results highlights – Publications:
S. Kment, P. Schmuki, Z. Hubicka, L. Machala, R. Kirchgeorg, N. Liu, L. Wang, K. Lee, J. Olejnicek, M. Cada, I. Gregora, R. Zboril: Photoanodes with Fully Controllable Texture: The Enhanced Water Splitting Efficiency of Thin Hematite Films Exhibiting Solely (110) Crystal Orientation, ACS NANO vol. 9, iss. 7, pp. 7113-7123, 2017.
S. Kment, Z. Hubicka, J. Krysa, D. Sekora, M. Zlamal, J. Olejnicek, M. Cada, P. Ksirova, Z. Remes, P. Schmuki, E. Schubert, R. Zboril: On the improvement of PEC activity of hematite thin films deposited by high-power pulsed magnetron sputtering method, APPLIED CATALYSIS B: ENVIRONMENTAL vol. 165, pp. 344-350, 2017.
A. Naldoni, U. Guler, Z. Wang, M. Marelli, F. Malara, X. Meng, L. V. Besteiro, A. O. Govorov, A. V. Kildishev, A. Boltasseva, V. M. Shalaev: Broadband Hot-Electron Collection for Solar Water Splitting with Plasmonic Titanium Nitride, ADVANCED OPTICAL MATERIALS vol. 5, iss. 15, pp. 1601031, 2017.
A. Naldoni, V. M. Shalaev, M. L. Brongersma: Applying plasmonics to a sustainable future, SCIENCE vol. 356, iss. 6341, pp. 908-909, 2017.
H. Han, F. Riboni, F. Karlicky, S. Kment, A. Goswami, P. Sudhagar, J. Yoo, L. Wang, O. Tomanec, M. Petr, O. Haderka, C. Terashima, A. Fujishima, P. Schmuki, R. Zboril: α-Fe2O3/TiO23D hierarchical nanostructures for enhanced photoelectrochemical water splitting, NANOSCALE vol. 9, iss. 1, pp. 134-142, 2017.
K. Jayaramulu, J. Masa, O. Tomanec, D. Peeters, V. Ranc, A. Schneemann, R. Zboril, W. Schuhmann, R. A. Fischer: Nanoporous Nitrogen-Doped Graphene Oxide/Nickel Sulfide Composite Sheets Derived from a Metal-Organic Framework as an Efficient Electrocatalyst for Hydrogen and Oxygen Evolution, ADVANCED FUNCTIONAL MATERIALS, pp. 1700451, 2017.
S. Kment, F. Riboni, S. Pausova, L. Wang, L. Wang, H. Han, Z. Hubicka, J. Krysa, P. Schmuki, R. Zboril: Photoanodes based on TiO2 and α-Fe2O3 for solar water splitting – superior role of 1D nanoarchitectures and of combined heterostructures, CHEM. SOC. REV. vol. 46, iss. 12, pp. 3716-3769, 2017.
K. Lee, A. Mazare, P. Schmuki: One-Dimensional Titanium Dioxide Nanomaterials: Nanotubes, CHEMICAL REVIEWS vol. 114, iss. 19, pp. 9385-9454, 2017.