Ordered mesoporous indium oxide nanocrystal (m-InO) was synthesized by nanocasting technique, in which highly ordered mesoporous silca (SBA-15) was used as structural matrix. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halanda (BJH) studies were carried out on m-InO and the results revealed that this material has a highly ordered mesoporous surface with reduced grain size, increased surface area and surface volume compared to the non porous indium oxide. The diffuse reluctance spectrum exhibited substantially improved light absorption efficiency in m-InO compared to normal indium oxide, however, no considerable change in the band gap energies of these materials was observed. When m-InO was used as a photo-catalyst in the photo-catalytic process of converting carbon dioxide (CO) into methanol under the pulsed laser radiation of 266-nm wavelengths, an enhanced photo-catalytic activity with the quantum efficiency of 4.5% and conversion efficiency of 46.3% were observed. It was found that the methanol production yield in this chemical process is as high as 485 µlg h after 150 min of irradiation, which is substantially higher than the yields reported in the literature. It is quite clear from the results that the introduction of mesoporosity in indium oxide, and the consequent enhancement of positive attributes required for a photo-catalyst, transformed photo-catalytically weak indium oxide into an effective photo-catalyst for the conversion of CO into methanol.
Supercapacitors are attracting great attention because of their fast charging-discharging ability as well as their high power density. The current research in this area focuses mainly on exploring novel low-cost electrode materials with higher energy and power densities. In this work, thin-film electrochemical capacitors were fabricated using layers of self-synthesized cadmium sulfide quantum dots and organometallic halide perovskite materials as active electrodes. Organometallic halide perovskites exhibit interesting ionic responses as well as extraordinary electronic properties. These properties are exploited in fabricating the electrochemical capacitors, and the devices showed excellent cycling ability with stable capacitance outputs beyond 4000 cycles. Impedance spectroscopy measurements revealed that perovskites do not only serve as active electrodes but also as solid electrolytes, thereby enhancing the capacitance of the devices and hence the energy densities. The layers provide high surface areas for electrolytes to access the electrode materials; reasonably low charge transfer resistance and small relaxation time were also observed. This work opens new opportunities for developing thin-film supercapacitors using low-cost electrode materials and employing a facile, inexpensive solution-process coating.
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