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ResearchNano-Power Field

Nano-Power Coordinator: Jinhua Ye

High efficiency materials and energy conversion system for a sustainable society

The key to efficient use of solar energy is the arrangement of the molecules responsible for various functions such as electron transport or reaction. For example, when converting, storing and transporting energy in photothermal or thermoelectric conversion materials, secondary cells, next-generation transistors, etc., the efficiency of ion and electron transport has a large effect, and control of atoms and molecules at interfaces is essential. In realizing high selectivity and efficiency in catalysts, which are indispensable for resource- and energy-saving chemical processes, how atoms and molecules are sequenced on the catalyst surface is key. In short, the scientific basis for realizing a sustainable society is designing the interfacial atomic and molecular arrangement corresponding to a specific purpose and carrying out the actual arrangement as designed -- in other words, “interfacial nanoarchitectonics”. Based on the concept of interfacial nanoarchitectonics, researchers in the Nano-Power Field are engaged in research and development for high efficiency matter-energy conversion by free manipulation of atoms and molecules and control of nanostructures.

Design and construction of advanced nano-photocatalytic materials for efficient solar to chemical energy conversion

By developing composition- and morphology-controlled nanometals and organic/inorganic semiconductor materials and hetero integration and hybridization of those materials, MANA aims to realize advanced utilization of sunlight and its efficient conversion to chemical energy. Also, through conducting fusion research between theoretical calculations and in-situ measurements, we are elucidating reaction mechanisms in order to provide crucial design guidelines for new material development. Our research target is to develop photocatalytic material technologies for advanced environmental purification and new energy production, and in particular, a way to convert CO2 to fuel.

High sunlight absorption and utilization, and selective conversion of CO2 to CO, were realized by creating a nano Fe catalyst derived from an organic metal framework encapsulated by carbon nanosheets. (Adv. Mater. 2016, DOI: 10.1002/adma.201505187)

Development of nanomaterials and devices for efficient energy transduction between light and heat

MANA is pushing forward with research to elucidate phenomena related to nanofocusing of electromagnetic energy at the surface and interface of nanoscale materials. We also study energy conversion phenomena, such as photoelectric and photothermal conversion, to establish methods for controlling visible and infrared light energy at the nanometer scale. Through the feedback between the simulation and the characterization, we develop nanostructure-controlled materials using physical, chemical and lithographic methods, developing materials and devices that realize high conversion efficiency between light, heat, and electricity.

(Left) Infrared emitter, which generates thermal emission (infrared beam) with a designated wavelength
(Right) Pyroelectric infrared detector (PIR), which produces electricity in response to a designated wavelength

Development of thermoelectric materials and thermal management technology utilizing nanostructure control and new principles

More than half of the primary energy consumed is waste heat. We have taken on the challenge of developing thermoelectric materials suitable for wide-scale applications for the first time ever, and also advanced thermal management technology, in order to use this enormous energy resource. To realize high thermoelectric performance by more effective selective scattering of phonons, we are developing a new nanostructure control technique, and are also elucidating various mechanisms at the atomic structural level, as shown in the figure. We are also searching for new principles, so we are now attempting to control thermoelectric properties through magnetism and design new high performance materials.

(Left) Mechanism of selective scattering of phonons due to atomic structure
(Right) An image of the thermoelectric enhancement effect of magnetism (coupling of carriers and magnons) and Seebeck coefficients of Cu1+xFe1-xS2

Creation of new materials and devices by functionalization of semiconductor nanostructures

By giving advanced composite functions to nanostructured semiconductor materials, we aim to realize new properties and outstanding functions in semiconductor materials. Since the Group IV elements silicon (Si) and germanium (Ge) are used as the main semiconductor materials, we are conducting research focusing on 1-dimensional nanowire structures and 0-dimensional quantum dots. As research targets, we are grappling with the development of a wide range of new materials and devices, from environmental and energy materials for generation and storage of electricity, etc., to the electronics field related to next-generation transistors that enable low power consumption.

(a) Scanning electron microscope image of nanowires formed on a silicon substrate
(b) Transmission electron microscope image of a germanium/silicon core-shell nanowire
(c) Results of composition analysis of the nanowire in (b) by energy dispersive X-ray spectrometry and a schematic diagram of a channel for use in a vertical transistor