探究超薄Bi2MoO6纳米片高效光催化CO2还原活性

铋系层状半导体材料凭借其独特的表面特性在光催化领域得到广泛的研究及应用，然而在光催化反应过程中光生电荷迁移及其表界面动态变化却鲜见报道。本文中，我们利用准原位X射线光电子能谱仪（QIS-XPS）系统研究超薄Bi2MoO6纳米片光催化CO2还原过程中光生电荷迁移及其表界面演变过程。研究结果表明：在暗态条件下CO2分子吸附于（010）暴露面Bi活性位，由于CO2分子强的拉电子能力，导致内层出现高价态Mo(6 x) 。当光照射至样品表面上时，*CO2峰显著降低，*CO峰明显升高，表明CO2分子在Bi活性位发生活化断键，并与光生电子反应形成*CO，使得高价态Mo(6 x) 含量增大。活性测试表明超薄Bi2MoO6纳米片的CO产量活性为41.8 ?mol g-1 h-1，其比块体Bi2MoO6活性高4.2倍，并且展现出优异的光催化稳定性。该工作为二维层状材料高效光催化CO2还原机理研究提供了一种全新的研究思路。

Unveiling the activity origin of ultrathin Bi2MoO6 nanosheets for photocatalytic CO2 reduction

Bismuth-based layer semiconductors have attracted particular attention for various photocatalytic applications, owing to their unique surface properties. However, the changes of photocharge migration and surface/interface structure during photocatalytic reactions are rarely reported. Herein, we first observe the dynamic evolution of photocharge migration and surface/interface structure over ultrathin Bi2MoO6 nanosheets during photocatalytic CO2 reduction via quasi-in situ X-ray photoelectron spectroscopy. Specifically, under the ground state, CO2 molecules adsorbed on the Bi activity site of the (010) exposed facet, owing to the strong electron-attraction of CO2 molecules, leading to the high-valance Mo(6 x) in the inner layer increase significantly. Upon light irradiation, the characterization of *CO2 significantly decreased, while the peak of *CO evidently increased, indicating that CO2 molecules activated, and transferred electrons from *CO, which increased the proportion of high-valance Mo(6 x) species. By virtue of the above unique characteristic changes, ultrathin Bi2MoO6 nanosheets exhibit excellent CO2 reduction to CO activity (41.8 ?mol g-1 h-1), which is nearly 4.2 times higher than that of bulk Bi2MoO6 nanosheets. Thus, this case provides new possibilities for photocatalyst design using two-dimensional materials with high solar-driven photocatalytic activity.