Research Topics

We have studied on advanced inorganic compounds: Polyoxometalates and Inorganic materials. We are very welcome to study as a postgraduate student under our supervision and/or do collaborated works with our compounds and related techniques. If you are interested in our works, feel free to send e-mail to us.
The details of our research topics are as follows.

A. Polyoxometalates:

Polyoxometalates(POMs), which consist of addenda atoms(tungsten, molybdenum, vanadium), hetero atoms (silicone, phosphorus, sulfur) and oxygen linking addenda atoms and hetero atoms, exhibit fascinating chemical properties: structure, catalysis, redox activity, photoactivity, magnetism and so on. They have been applied to a huge range of scientific and industrial fields on the basis of their chemical properties. They have been extensively studied for a long time but there are still a lot of unclear aspects. In order to clarify such ambiguous points, we have been studied on synthesis and characterization of novel polyoxometalates.

A-1. Synthesis of novel polyoxometalates

We have prepared novel polyoxometalates by using different hetero ions. A lot of novel metal-substituted tungstosulphates and organo-phosphates incorporating POMs have been prepared, isolated and characterized with various synthetic techniques.

A-2. Electrochemistry of POMs

Electrochemistry of POMs is very rich since many electrons transferred redox occurs without decomposition and many of POMs have been applied to important fields such as battery and water splitting based on their electrochemical properties. However there are still unclear aspects on the voltammetric behavior. We have tried to elucidate the detailed voltammetric behavior with simulation of cyclic voltammograms with a help of NMR, ESR and the other measurements.

A-3. Formation mechanism of POMs

Formation mechanism of POMs is very complicated although a huge number of POMs have been prepared until now. Because there are a lot of factors needed to be considered: concentrations, pH, temperature, reaction time, solvents and so on.

A-4. (Analytical) application of POMs

Formation reaction and reduction of POMs have been used for spectrophotometric determination of phosphorus and silica, so called molybdenum blue method and molybdenum yellow method. Achievements of our studies on POMs improved sensitivity in molybdenum blue method. In addition, electrochemical method of antioxidant capacity has been developed to measure more easily than the reported methods: ORAC and DPPH.

B. Development of highly active catalyst for hydrogen and chemicals productions from unutilized feedstocks

Natural gas and biomass are inexpensive and abundant feedstocks, but there are limited to utilize for chemicals production due to their high stability. We focus on developments of highly active catalysts for hydrogen and valuable chemicals (e.g. olefins and aromatics) productions from these feedstocks. We also investigate the low-temperature catalytic reaction systems to utilize an unutilized low-temperature waste heat.

For example, although oxidative coupling of methane is useful catalytic reaction to produce ethylene directly from methane and oxygen (eq. 1), it usually require high reaction temperature above 700 °C.
2CH4　+　O2　→　C2H4　+　2H2O　(eq. 1)
On the contrary, it was found that application of an electric field to Ce2(WO4)3/CeO2 catalysts, which was prepared from polyoxometalate, enabled to proceed oxidative coupling of methane with high activity even at low temperature of 150 °C.

Thus, we are studying novel catalysts and low-temperature reaction-field for efficient productions of energy and chemicals in next-generation.