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【答案】应助回帖
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220chengeng: 金币-5, 违规存档, 请勿抄袭。 2012-12-28 16:37:02
This is because the aluminium ion doping, ZnO particle size was fine. Nanometer zinc oxide particle size becomes smaller, the energy gap widens, the conduction band and valence band becomes more negative potential, potential becomes corrections, get stronger redox ability, thus improve the photocatalytic activity. At the same time, nanometer zinc oxide with decreasing the particle size, surface area is increased, the adsorption substrate ability enhancement, can promote the photocatalytic reaction of. In addition, from the chemical point of view, dopant ions is effective electron acceptor, can capture the electrons in the conduction band. Because the ion doping on electronic contention, reduce the surface of the semiconductor optical electronic e- and photoinduced hole h+ compound, so that the surface of the semiconductor to produce more 0H and O2, increase the activity of the catalyst . Aluminum ion doped to become the electron-hole capture trap, can reduce the electron and hole composite, extended OH life. When doping concentration less than optimal amount, with the doping quantity increase, doping ions provided capture trap number increases, the electron - hole recombination suppression ability enhancement, photocatalytic ability improvement . When it is greater than the best quantity, due to capture carrier capture a distance between small, dopant ions become electron-hole recombination center, and the larger amount of dopant may also make the dopant ions in ZnO saturation and produce new phase, reducing the ZnO of the effective surface area, thereby affecting photocatalytic efficiency. The microstructure and lattice distortion of view, Al3+ doped with Z n O matrix, a may be aluminum ion substitution of metal ions Z n, another may be aluminum ion in matrix Z nO gap position. Because the aluminum ion radius 0.054nm than zinc ion radius 0.074 nm small, thus causing local lattice distortion, the Al doped Z n O band structure change, gap width, thereby improving Z n O redox ability. In addition, due to the presence of large lattice distortion and strain energy, to compensate for the lattice strain, Z n O character of surface oxygen atom lattice so as to easily escape hole trapping effect, reduce the electron-hole pair recombination rate, thus improve the photocatalytic activity of O Z n.
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