Visualizing the Nano Cocatalyst Aligned Electric Fields on Single Photocatalyst Particles
Visualizing the Nano Cocatalyst Aligned Electric Fields on Single Photocatalyst Particles
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可视化单个光催化剂颗粒上的纳米助催化剂排列电场
DOI：
10.1021/acs.nanolett.7b02799
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发表时间：
2017-11-01
期刊：
影响因子：
10.8
通讯作者：
Li, Can
中科院分区：
文献类型：
--
作者：
Zhu, Jian;Pang, Shan;Li, Can
光催化剂的助催化剂或双助催化剂是高效人工光合作用生产太阳能燃料不可缺少的。然而，由于光生电荷参与了光催化反应的基本步骤，因此助催化剂增加的反应活性不能直接归因于加速的催化动力学。到目前为止，关于助催化剂的不同观点表明，它们对β-环糊精的确切作用还没有很好地理解。在这里，我们直接图像的光生电荷载流子的局部分离跨单晶的BiVO 4光催化剂，其局部负载的MnOx单助催化剂的纳米颗粒或与空间上分离的MnOx和Pt双助催化剂的纳米颗粒。单一助催化剂的沉积不仅导致界面电荷转移的强烈增加，而且令人惊讶地导致光催化剂未覆盖表面下方的内置电场方向的改变。外加电场引起局部表面光电压信号的强烈增加（高达80倍），并与光催化性能的增加相关。通过空间分离的双助催化剂的协同效应，局部电场进一步增加（高达2.5 kV.cm（-1））。结果表明，助催化剂通过调整光催化剂颗粒内建电场的矢量，对光催化剂颗粒内的电荷分离起决定性作用。这种效果超出了它在热催化中的催化功能。
The cocatalysts or dual cocatalysts of photocatalysts are indispensable for high efficiency in artificial photosynthesis for solar fuel production. However, the reaction activity increased by cocatalysts cannot be directly ascribed to the accelerated catalytic kinetics, since photogenerated charges are involved in the elementary steps of photocatalytic reactions. To date, diverging views about cocatalysts show that their exact role for photocatalysis is not well understood yet. Herein, we image directly the local separation of photogenerated charge carriers across single crystals of the BiVO4 photocatalyst which loaded locally with nanoparticles of a MnOx single cocatalyst or with nanoparticles of a spatially separated MnOx and Pt dual cocatalyst. The deposition of the single cocatalyst resulted not only in a strong increase of the interfacial charge transfer but also, surprisingly, in a change of the direction of built-in electric fields beneath the uncovered surface of the photocatalyst. The additive electric fields caused a strong increase of local surface photovoltage signals (up to 80 times) and correlated with the increase of the photocatalytic performance. The local electric fields were further increased (up to 2.5 kV.cm(-1)) by a synergetic effect of the spatially separated dual cocatalysts. The results reveal that cocatalyst has a conclusive effect on charge separation in photocatalyst particle by aligning the vectors of built-in electric fields in the photocatalyst particle. This effect is beyond its catalytic function in thermal catalysis.