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【答案】应助回帖
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sltmac: 金币+10 2012-12-28 12:47:30
However with the sodium doped quantity increase, catalyst degradation activity also increases gradually, when the doping of 15%, active returned to levels comparable with pure ZnO. This is because the Na doped ZnO can generate Nai+ and NaZn- the two impurity defects, dopant in the initial stage, the Fermi level is larger, NaZn- formation can be less than Nai+, will give priority to generate NaZn-, formed acceptor defect levels, resulting in the increase of the concentration of ZnO hole, type N optical response is weakened, photocatalytic activity drop. Simultaneous formation of the acceptor level is the light induced electron contenders, thus inhibiting the catalyst surface of photogenerated electrons and holes of the yield, photocatalytic activity decline. However in the hole density increase while the Fermi level will gradually decrease, leading to the formation of NaZn- can rise, Nai+ can drop formation. So further increased dopant concentration, can lead to the generation of Nai+, self compensation effect, so that the hole concentration decreased. Type N optical response due to recovery, photocatalytic activity came back.
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