State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China.
Photoactivated Processes Unit, IMDEA Energy Institute, Avda. Ramón de la Sagra 3, 28935 Móstoles Madrid, Spain.
ACS Appl Mater Interfaces. 2023 Jun 14;15(23):28739-28746. doi: 10.1021/acsami.3c02783. Epub 2023 May 30.
Forming semiconductor heterojunctions is a promising strategy to boost the efficiency of solar-driven photoelectrochemical (PEC) water splitting by accelerating the separation and transport of photogenerated charge carriers via an interfacial electric field. However, there is limited research considering the influence of electrolytes on the band alignment of the heterojunction under PEC conditions. In this work, we use a single crystal NiCoO/SrTiO (NCO/STO) heterojunction with atomic-precision controlled thickness as a model photoelectrode to study the band structure modulations upon getting in contact with the electrolyte and the correlation with the PEC activity. It is found that the band alignment can be tuned by the control of p-n heterojunction film thickness and regulated by the water redox potential (). When the Fermi level () of the heterojunction is higher/lower than the , the band bending at the NCO/STO-electrolyte interface will increase/decrease after contacting with the electrolyte. However, when the band bending width of the NCO layer is thinner than its thickness, the electrolyte will not influence the band alignment at the NCO/STO interface. In addition, PEC characterization results show that the 1 nm NCO/STO heterojunction photoanode exhibits superior water-splitting performance, owing to the optimum band structure of the p-n heterojunction and the shorter charge transfer distance.
形成半导体异质结是一种很有前途的策略，可以通过界面电场加速光生载流子的分离和输运，从而提高太阳能驱动光电化学（PEC）水分解的效率。然而，在 PEC 条件下，考虑电解质对异质结能带排列的影响的研究还很有限。在这项工作中，我们使用具有原子精度控制厚度的单晶 NiCoO/SrTiO（NCO/STO）异质结作为模型光电极，研究了与电解质接触时能带结构的调制及其与 PEC 活性的相关性。结果发现，通过控制 p-n 异质结薄膜厚度可以对能带排列进行调节，并受水氧化还原电位（）的调控。当异质结的费米能级（）高于/低于时，与电解质接触后，NCO/STO 界面处的能带弯曲会增加/减小。然而，当 NCO 层的能带弯曲宽度小于其厚度时，电解质不会影响 NCO/STO 界面处的能带排列。此外，PEC 特性测试结果表明，1nm NCO/STO 异质结光阳极具有优异的水分解性能，这归因于 p-n 异质结的最佳能带结构和较短的电荷转移距离。
