Nagoya Institute of Technology in Japan has developed a process for synthesizing composite particles of molybdenum oxide and carbon.
Seawater desalination technology using interfacial solar steam generation (ISVG) is regarded as an economical and clean process of producing drinking water; hence, it was recognized as a hot word. This Nagoya Institute of Technology technology used solar energy input that was absorbed by heat which was trapped near the water surface creating freshwater incredibly efficient at evaporating water. The existing concerns are light absorption range limitations of the photothermal conversion catalysts whereby improvement of energy conversion efficiencies remains one of the challenges.
The Institute of Technology of Nagoya in Japan has induced a process that can synthesize a moistened molybdenum oxide and carbon composite particles at normal temperature and in limited time. Molybdenum oxide under visible light shows excellent light absorption ability in the near-infrared region. The Institute of Technology of Nagoya intends to dope commercially available MoO3 with hydrogen ions in this study to synthesize meso-stabilized MoOx (HxMoO3-y and MoO2).
As a new synthesis method, the research team focused on the mechano-chemical process, treating polypropylene (PP), a common plastic, with commercially available molybdenum oxide for a short time to synthesize composite particles of molybdenum oxide and carbon at room temperature. The research team evaluated the reaction mechanism by evaluating or analyzing the structure of the synthesized material, theoretical calculation of the processing energy, and investigating the dependence of the degassing behavior on the synthesis conditions, and confirmed that the reaction between the materials (MoO3-PP) promoted the decomposition of PP and the reduction of molybdenum oxide, and that PP was converted into carbon during the reaction process to form a composite structure.
The newly developed composite particles show high light absorption in the ultraviolet to near-infrared region of 200 to 2,000 nm. In addition, when the experimental photothermal conversion catalyst carrier sheet was floated on the water surface and irradiated with near-infrared light, the temperature immediately rose and the local temperature near the water surface became high. In addition to the water evaporation rate reaching 3.29 kg m-2 h-1, it was confirmed that its energy conversion efficiency was about 90% and it had long-term stability.
On the other hand, due to the formation of the composite structure, the photocatalyst function of converting light energy into chemical reactions was also demonstrated. It has been confirmed that by promoting the oxidative decomposition of the photocatalyst function, azo dye-type pollutants (methyl orange) can be decomposed and removed in a short time under visible light or near-infrared irradiation.
In addition, through the results of the identification of the photocatalytic reaction mechanism and the evaluation of the electronic structure of the synthesized material, it is known that controlling the composition of the MoOx phase is very important for maximizing performance. Furthermore, it was confirmed that pollutants or heavy metals can be removed efficiently even in the absence of light irradiation. After analysis, it was confirmed that the surface structure of the by-product carbon contributes to the improvement of acid catalyst function or ion adsorption capacity.
By using the newly developed technology, stable performance can be achieved even when sunlight cannot be used, and further promote the development of stable drinking water supply technology. In addition, the mechanochemical process used in this study can be applied to any type of plastic or oxide, and is expected to help improve the function of existing raw materials and promote the upcycling of waste plastics.
In the future, the research team will evaluate the equipment specifications that can achieve stable quality while expanding the scale of the synthesis process, invest in the analysis of the chemical structure or limiting environmental factors that determine multifunctionality, and promote the construction of large-scale pilot systems or outdoor verification, in order to expand the practical possibilities of desalination technology using next-generation catalysts.
