Effects of Nonstoichiometry and Cocatalyst Loading on the Photocatalytic Hydrogen Production with (Y1.5Bi0.5)1−xTi2O7−3x and (YBi)1−xTi2O7−3x Pyrochlores
Effects of Nonstoichiometry and Cocatalyst Loading on the Photocatalytic Hydrogen Production with (Y1.5Bi0.5)1−xTi2O7−3x and (YBi)1−xTi2O7−3x Pyrochlores
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DOI：
10.1111/jace.12013
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发表时间：
2013-02
影响因子：
3.9
通讯作者：
O. Merka;O. Raisch;F. Steinbach;D. Bahnemann;M. Wark
中科院分区：
文献类型：
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作者：
O. Merka;O. Raisch;F. Steinbach;D. Bahnemann;M. Wark
通过调节合成过程中的Ti/(Y+Bi)比，用水相溶胶-凝胶法制备了(Y1.5Bi0.5)1−xTi2O7−3x和(YBI)1−xTi2O7−3x的非化学计量焦绿石，并在不同温度下进行了热处理。用X-射线衍射仪和紫外可见光谱对材料进行了表征。在以甲醇为牺牲剂的情况下，负载了作为助催化剂的纳米Rh或Ph后，对样品进行了光催化制氢性能测试。研究发现，通过优化Ti/(Y+Bi)的比例，可以将化学计量组成完全不活跃的材料调整为良好的光催化剂。活性的增加被认为是由于结构内产生空位而优化了TiO6-八面体几何结构。增加铋的负载量会将吸收边转移到可见光，但不幸的是，增加结构中的铋含量也会导致光催化过程中的稳定性问题，而较高的助催化剂负载量可以抑制或至少削弱这种稳定性。
By adjusting the Ti/(Y+Bi) ratios during synthesis, nonstoichiometric pyrochlores of (Y1.5Bi0.5)1−xTi2O7−3x and (YBi)1−xTi2O7−3x were prepared by an aqueous sol–gel method and annealed at different temperatures. The materials were characterized by X-ray diffraction and UV–vis reflectance spectroscopy. The samples were tested for photocatalytic hydrogen production in the presence of methanol as sacrificial agent after being loaded with nanoparticles of rhodium or platinum acting as cocatalysts. It was found that materials being completely inactive in a stoichiometric composition can be tuned to good photocatalysts by optimizing the Ti/(Y+Bi) ratio. The increase in activity is supposed to derive from an optimization of the TiO6-octahedral geometry due to the generation of vacancies inside the structure. Increasing the Bi loading shifts the absorption edge into the visible, but unfortunately, an increase of the bismuth content in the structure also leads to stability issues during photocatalysis, which can be suppressed or at least weakened by a higher cocatalyst loading.