Download or read book High Efficiency Photochemical Water Splitting on III-nitride Nanowires written by Md Kibria and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The conversion of solar energy into hydrogen via water splitting process is one of the key sustainable technologies for future clean, storable and renewable source of energy. Therefore, development of stable and efficient photocatalyst material has been of immense interest, but with limited success. Here, we show that overall neutral water splitting can be achieved under ultraviolet (UV) and visible light irradiation using group-III nitride nanowire arrays grown by plasma-assisted molecular beam epitaxy. The Rhodium/Chromium-oxide core/shell nanoparticle decorated GaN nanowires show stable photocatalytic activity under UV irradiation, with the turnover number well exceeding any previously reported GaN particulate samples. Additionally, by tuning the surface Fermi-level with controlled Mg doping in GaN nanowires, we demonstrate that the internal quantum efficiency can be enhanced by nearly two orders of magnitude under UV irradiation. Furthermore, in order to utilize the abundant visible solar spectrum, we have designed a multi-band InGaN/GaN nanowire heterostructure, that can lead to stable hydrogen production from neutral (pH~7.0) water splitting under UV, blue and green light irradiation (up to ~ 560 nm), the longest wavelength ever reported. At ~440-450 nm wavelengths, the internal quantum efficiency is estimated to be ~ 13%. Moreover, we have designed a dual-band p-type InGaN/GaN nanowire heterostructure, wherein Mg doping is optimized both in GaN and InGaN nanowires to achieve stable and efficient overall water splitting under UV and visible light. An internal quantum efficiency of ~69% has been achieved for neutral (pH~7.0) water splitting, the highest value ever reported under visible light illumination (400-475 nm). Subsequently, we have demonstrated that the optical absorption edge of GaN nanowires can be reduced from 3.4 eV to 2.95 eV by introducing Mg-related acceptor and nitrogen vacancy related donor energy states. This band-engineered GaN nanowires exhibit stable overall water splitting under violet light (up to 450 nm). The internal quantum efficiency of Mg doped GaN nanowire reached ~43% at 375-450 nm. Detailed analysis further confirms the stable photocatalytic activity of the III-nanowire heterostructures. Finally, we have presented the first example of dye-sensitized InGaN nanowires for Hydrogen generation under green, yellow and orange solar spectrum (up to 610 nm). This work establishes the use of metal-nitrides as viable photocatalyst for solar-powered artificial photosynthesis for future large-scale hydrogen and methanol based economy." --