■ Energy storage using ice-like and sponge-like materials
Hydrogen, one of the promising future energy options, has been explored in a variety of science fields to extract any potential solutions, but unfortunately all the existing technologies using compressed hydrogen, metal hydride, carbonaceous materials, and MOF have not been successful because of their inherent limitations such as storing capacity, operation condition, and storage material weight. Accordingly, one definite breakthrough technology is urgently needed to provide future energy resource and build hydrogen-based society. In this connection, the green and novel ice or ice-like materials are proposed as the hydrogen storing media because these crystalline hydrates or clathrates create tremendous empty cages in which hydrogen molecules are entrapped. This ice-based hydrogen storage method only requires the mild temperature and pressure condition, but for practical application more researches to overcome the technical barriers should be done using macroscopic and microscopic approaches. The ultimate energy storage and transportation goal is to synthesize the sponge-like materials that can readily absorb and release the energy gas, breaking from the conventional approaches with the aid of genuine break-through concepts.
■ Frontier energy devices using host-guest networks
The inclusion phenomena are introduced in developing functional energy devices with specific-target functions. In particular, pure and mixed ionic clathrates or liquids are synthesized to manufacture fuel cell electrolytes, magnetic materials and other energy-related specialty materials. The first goal is to establish the basic principles of ice engineering for the better understanding of new genre in physical chemistry. Highly advanced spectroscopic methods are actively used, such as solid-state NMR, in-situ Raman, MRI, and neutron and X-ray diffractions. Versatile host and guest molecules are specially designed and synthesized to build the host-based frameworks in which nano-cages or nano-channels for guest molecules to pass through are formed. Moreover, structural transitions accompanying with coexistence of multi clathrate structures are carefully investigated to enhance the key physicochemical properties needed for the target-purpose energy devices. This unique approach can greatly contribute to inclusion chemistry and future energy fields.
■ Swapping exhaust for fuel
When carbon dioxide, one of the global warming gas, itself is put under certain pressure, a solid carbon dioxide hydrate can be formed according to the stability regime. On the other hand, large amounts of methane in the form of solid hydrates are deposited on continental margins and in permafrost regions and more importantly receive world-wide attention as a hidden future energy resource. However, the existing production technologies such as depressurization, thermal stimulation and hydrate inhibitor for recovering methane gas from methane hydrate deposits buried on deep ocean floor fail to be adopted because of their serious damage on marine ecosystem. Hopefully, the direct swapping between carbon dioxide and methane might overcome this environmental concern and moreover provide actual production process merits over the conventional ones. If methane hydrates could be converted into carbon dioxide hydrates, they would serve double duty as methane sources and carbon dioxide sequestering sites. Such a simultaneously-occurring dual mechanism of carbon dioxide sequestration and methane recovery is expected to provide the physicochemical background required for developing a promising large-scale approach with economic feasibility. Further, we explore the more efficient and real swapping phenomenon occurring in methane hydrate deposits and its potential application to carbon dioxide sequestration, considering the direct use of flue gas mainly consisting of carbon dioxide and nitrogen.
Huen Lee (이흔)
KEPCO Chair, Professor