Characterization of ball-milled bismuth vanadate and transition metal oxide nanoparticles
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Photoelectrochemical (PEC) water splitting has been widely accepted as a favorable approach for hydrogen production using solar energy. Bismuth vanadate, or BiVO4, is considered an efficient and stable photoelectrode material. Most importantly, the appropriate band gap (~2.4eV) allows BiVO¬4 to absorb a substantial portion of the incident solar spectrum including visible light. The particle properties play a critical role in the efficiency of H2 production. VO2 has drawn extensive attention in the optoelectronic field because the electrical conductivity of VO2 can change by several orders of magnitude by going through a metal-insulator-transition (MIT) temperature. Therefore, structural characterization and nanoparticle analysis are essential for both materials’ preparation and applications in the future. The BiVO4 and VO2 sample solutions are prepared by milling sample powder with ricinoleic acid for 3 hours and adding in a water-toluene mixture. These samples were then characterized by Transmission Electron Microscope (TEM), Selected Area Electron Diffraction (SAED) and Energy Dispersive Spectrometry (EDS). The results of TEM reveal that the size and shape of the nanoparticles could be controlled by the synthesis parameters such as suspension period and concentration of the vanadium solution. Concurrently, the positive identification of the chemical elements and the interpretation of the EDS data also reveal only Bi, V and O elements in the samples. The preparation of nanoparticles by ball milling may lead more broadly to novel properties from known materials.