Mn-doped TiO2 photocatalysts: Role, chemical identity, and local structure of dopant
Mn-doped TiO2 photocatalysts: Role, chemical identity, and local structure of dopant
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DOI：
10.1016/j.jpcs.2020.109517
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发表时间：
2020-09
影响因子：
4
通讯作者：
Hanggara Sudrajat;S. Babel;A. Ta;T. Nguyen
中科院分区：
文献类型：
--
作者：
Hanggara Sudrajat;S. Babel;A. Ta;T. Nguyen
通过水热法掺杂Mn，使TiO 2的光响应扩展到可见光。全面阐明了Mn掺杂剂的作用、化学身份和局部结构，以找到改善光催化活性的关键因素。X射线吸收精细结构和同步辐射X射线近边结构谱表明，Mn掺杂部分取代了TiO 2基体中的Ti原子，形成了MnO 2-TiO 2固溶体。Mn掺杂剂将主体的光吸收扩展到可见光区域并限制电子-空穴复合，如分别通过漫反射光谱和光诱导红外吸收光谱探测的。光吸收的扩展与光催化活性的提高不是单调相关的。在过量的Mn浓度下，导带边缘底部变得太低而不能通过光激发电子还原吸附的氧。未消耗的电子最终与空穴复合以加速复合，导致低电子布居。在扩展的光吸收和复合之间存在折衷。这在4wt%的Mn浓度下优化，以产生最高的电子数，并因此产生最高的光催化活性。
The response of TiO2is extended to visible light by doping with Mn through a hydrothermal route. The role, chemical identity, and local structure of the Mn dopants are comprehensively elucidated to find the key factors behind the improved photocatalytic activity. X-ray absorption fine structure and X-ray near-edge structure spectroscopy with synchrotron light reveal that the Mn dopants partially replace Ti atoms in the bulk of the TiO2host to form a MnO2–TiO2solid solution. The Mn dopants extend the light absorption of the host to the visible region and restrict electron-hole recombination, as probed by diffuse reflectance spectroscopy and light-induced infrared absorption spectroscopy, respectively. The extension of light absorption is not monotonically correlated with the improvement in photocatalytic activity. At an excessive Mn concentration, the conduction band edge bottom becomes too low to enable the reduction of the adsorbed oxygen by the photoexcited electrons. The unconsumed electrons eventually recombine with holes to accelerate the recombination, resulting in a low electron population. There is a trade-off between the extended light absorption and the recombination. This is optimized at a Mn concentration of 4 wt%, to yield the highest electron population, and thus, the highest photocatalytic activity.