TOPIC 1.- ENERGY STORAGE AND CONVERSION Multiredox nanoclusters/ nanoparticles for enhanced oxygen redox reactions in metal-air batteries (D.Tonti and N. Casañ) Engineering the Solar Spectrum with Photonic Architectures for Improved Solar Energy Conversion (A. Mihi and A. Goñi) Laser synthesis of carbon-based nanocomposites for energy-storage applications (A. Pérez and E. György) Organic/inorganic hybrid materials for photovoltaic/thermoelectric hybrid applications (A. R. Goñi, M.I. Alonso and M. Campoy-Quiles)
Multiredox nanoclusters/ nanoparticles for enhanced oxygen redox reactions in metal-air batteries Supervisors: Dr. Dino Tonti and Dr. Nieves Casañ-Pastor Abstract: Non-aqueous Li/O2 batteries are among the most promising novel battery chemistries. They could allow 3-5 times the specific energy of current Li-ion batteries (considered capable to reach 200 kwh/kg at most) while significantly lowering their cost. In spite of intense investigation efforts in the past few years still their performance and durability are not satisfactory to establish as a technology. This is mostly attributed to the lack of an optimal control of the complex reduction processes of oxygen that need to take place quickly and reversibly, similar to what is also required in fuel cells. The discharge reaction implies the formation of a passivating lithium peroxide within the pores of the electrode, frustrating rechargeability and cycle life. Remarkable improvements can be achieved by alternative paths involving soluble catalysts (redox mediators, RM) in the electrolytes. Given its potential for a practical device, research for stable and effective mediators is being actively investigated. We propose the use of multiredox nanosized oxides, such as polyoxometalate clusters or other nanoparticles such as FeOx, IrOx as RM. These oxides are already known by their reversible redox activity in oxidation and reduction processes and in many cases by their catalytic activity, which would add a second advantage in O2 reduction process. This work, by aiming to the development of efficient and stable redox mediators for Metal/air batteries, has three main objectives: 1) elucidation of existing and novel electrode mechanisms, 2) finding of alternative cheaper materials and 3) development of high energy storage devices. Y. Tesio, D. Blasi, M. Olivares-Marín, I. Ratera, D. Tonti and J. Veciana Organic radicals for the enhancement of oxygen reduction reaction in Li O2 batteries Chemical Communications, 51 (2015) 17623-17626 N. M. Carretero, M. P. Lichtenstein, E. Pérez, S. Sandoval, G. Tobias, C. Suñol, N. Casan-Pastor. Enhanced Charge Capacity in Iridium Oxide-Graphene Oxide Hybrids Electrochimica Acta 157 (2015) 369-377
Engineering the Solar Spectrum with Photonic Architectures for Improved Solar Energy Conversion. Supervisors: Dr. Agustín Mihi and Prof. Alejandro R. Goñi Abstract: Many types of solar cells have been developed from wafer based to polymer based devices with appealing advantages for different applications. However, all these photovoltaic technologies share the same limiting maximum efficiency for single junction solar cells: the Shockley-Queisser limit. Basically, given the energy distribution in the solar spectrum, the choice of the band gap in a single junction device is a question of balancing two types of energy losses; the energy lost by those photons more energetic than the band gap of the semiconductor (thermalization losses) and those photons without sufficient energy to promote electrons from the valence band across the gap of the material. Under these circumstances, the maximum efficiency a solar cell could achieve without concentration is around 30% with a bandgap at 1.34 ev. An interesting alternative has appeared recently, where the emphasis is placed in engineering the solar spectrum rather than reimagining the device. Up and down conversion, luminescent concentrators and thermo-photovoltaics (TPV) introduce a new element between the sun and the cell capable of reengineering the solar spectrum irradiating the device. In TPV, for instance, the intermediate absorber/emitter will absorb the sun radiation (absorber part) and re-emit the energy (emitter part) in a much narrow spectral distribution, centered at the band gap of the solar cell. This strategy could lead to theoretical maximum power conversion efficiencies up to 80%, depending on the emitter temperature. The main tasks to be developed by the FPI fellow are: 1) The design and fabrication of absorber/emitter architectures based on photonic crystals capable of reshaping the solar spectrum [1]. Their optical properties can be simulated by means of finite differences time domain (FDTD) software. Fabrication of prototypes will be based on combination of low-cost techniques (soft lithography, solution processing and self-assembly). 2) Characterization of the photonic architectures. Far-field rejections (reflectance / transmittance) will be acquired by means of VIS-NIR-MIR spectrophotometry. The near-field electric field spatial distributions will be inspected via SNOM [2]. 3) Implementation in real devices and device testing. The validity of this strategy will be explored with real devices such as a hybrid thermos-photovoltaic solar cell and/or a thermal radiation detector. [1] Radiative lifetime modification of LaF3: Nd nanoparticles embedded in 3D silicon photonic crystals. H Ning, A Mihi, et al. Adv. Mater. 24 (2012) OP153 OP158 [2] Spatial distribution of optical near-fields in plasmonic gold sphere-segment voids. M. Schmidt, N.G. Tognalli, M.A. Otte, M.I. Alonso, B. Sepúlveda, A. Fainstein, and A. R. Goñi; Plasmonics 8 (2013) 921-930
Laser synthesis of carbon-based nanocomposites for energy-storage applications Supervisors: Dr. Enikö György and Dr. Ángel Pérez del Pino Abstract: Major research and industrial efforts are focused to obtain renewable energy sources with higher efficiency and lower costs. However, the difficulty to storage the high amount of generated renewable energy set out significant problems for their implementation. Recent research works point to nanocarbonbased electrodes as strategic elements for future high-performance electrochemical energy storage devices. Vertically aligned carbon nanotubes (VACNTs) and graphene are especially suitable for energy storage devices due to their high surface area and high conductivity. The aim of the proposal is to produce carbon-based hybrid nanostructures and thin films on flexible metallic electrodes, using earth-abundant, low cost and eco-friendly materials for the production of high performance electrochemical energy storage devices. In particular, versatile and novel laser methodologies (laser direct write and matrix assisted pulsed laser evaporation) will be used to obtain carbon nanostructures / metal oxides (MeO) nanocomposite films (based on VACNTs, reduced graphene oxide (rgo), and MeO). Recently, the Laser Processing Research Group at ICMAB has achieved very promising results on the photoreduction of graphene oxide (GO) and GO-MeO nanocomposites by laser irradiation. The suitable combination of laser-based technologies will offer the possibility to produce electrodes with high energy storage density, high capacitance/mass ratio, and more stable life-cycles. These techniques are expected to be of low-cost and easy to integrate in industrial processes. In particular, the methods applied in this proposal will put forward new ways in order to fabricate CNT- and graphene-based hybrid nanocomposite electrodes eluding many problems related to conventional synthesis methods with complex, expensive and toxic pathways. The work will be carried out in the frame of a MINECO Societal Challenge project. Pérez del Pino, et al. Laser-induced chemical transformation of graphene oxide iron oxide nanoparticles composites deposited on polymer substrates. Carbon 2015, 93, 373 383. S. M. O Malley, et al. Resonant Infrared and Ultraviolet Matrix-Assisted Pulsed Laser Evaporation of Titanium Oxide/Graphene Oxide Composites: A Comparative Study. J. Phys. Chem. C 2014, 118, 27911 27919
Organic/inorganic hybrid materials for photovoltaic/thermoelectric hybrid applications Supervisors: Prof. Alejandro R. Goñi, Dr. M. Isabel Alonso and Dr. Mariano Campoy-Quiles Abstract: Amongst the different alternatives for renewable energy production, photovoltaic (PV) and thermoelectric (TE) technologies are being increasingly developed with the aim of playing a larger role in the future energy mix. This is so for small and medium-scale energy generation/harvesting and for standalone applications. Furthermore, synergic properties and enhanced performance emerge when combining different but complementary materials into composites (e.g. hybrid materials). The aim of this proposal is twofold: Advance novel hybrid materials [1, 2] and develop hybrid photovoltaic/thermoelectric applications. This proposal is well suited for training students in an increasingly important academic field, relevant also for their potential future employment in the nascent industry associated to green energy production via emerging photovoltaics and thermoelectrics. The prospective FPI fellow would be trained in a broad range of skills reflecting the multidisciplinary nature of the field, including relevant aspects from chemistry, physics, material science and engineering as well as in the processing of organic and inorganic semiconductors for solar cells and thermoelectric devices. This will require mastering a variety of methods that will be carried out in high-tech controlled environments often employed in the semiconductor industry (clean room class 10.000 and inert gas filled glovebox). The work plan to be developed by the fellow includes: - To contribute to engineering the different processing methods and protocols in order to produce hybrid materials with improved PV/TE properties. - To use several techniques for the characterization of the PV and TE properties of the produced materials and devices: full electrical transport characterization, thermopower measurement, ellipsometry, photoluminescence, Raman microscopy, photocurrent mapping, external quantum efficiency and photovoltaic power conversion measurements. - To design, simulate, fabricate and optimize hybrid PV/TE devices. [1] B. Dörling, J. D. Ryan, M. C. Weisenberger, A. Sorrentino, A. El Basati, A. Gomez, M. Garriga, E. Pereiro, J. E. Anthony, A. R. Goñi, C. Müller, and M. Campoy-Quiles, Photoinduced p- to n-type Switching in Thermoelectric Polymer-Carbon Nanotube Composites; Adv. Mater. (2016). DOI: 10.1002/adma.201505521 [2] A. M. A. Leguy, A. R. Goñi, J. M. Frost, J. Skelton, F. Brivio, X. Rodríguez-Martínez, O. J. Weber, A. Pallipurath, J. Sibik, A. Zeitler, M. I. Alonso, M. Campoy-Quiles, M. T. Weller, J. Nelson, A. Walsh, and P. R.F. Barnes, Phonon Lifetimes, Dynamic Disorder and the Assignment of Modes to the Vibrational Spectra of Methylammonium Lead Halide Perovskites; submitted to Mater. Horizons (2016).