Abstract：
The low efficiency of photocatalytic hydrogen production from water is mainly suffer from limited light absorption, charge separation and water delivery to the active centers. Herein, an inorganic-organic Z-scheme heterojunction (CdS-COF-Ni) is constructed by in-situ growth of CdS nanosheets on the porphyrin-based covalent organic framework with nickel ions (COF-Ni) in the porphyrin centers. A built-in electric field is formed at the interface, which accelerates the separation and transfer of photogenerated charges. Moreover, through the surface protonation treatment in ascorbic acid (AC) solution, the hydrophilicity of the obtained composite is obviously increased and facilitates the transport of water molecules to the photocatalytic centers. Under the synergistic effect of the interfacial interaction and surface protonation treatment, the photocatalytic hydrogen production rate is optimized to be 18.23 mmol h-1 g-1 without adding any cocatalysts, which is 21 times that of CdS. After a series of photoelectrochemical measurements, in situ X-ray photoelectron spectroscopy (XPS) analysis, and density functional theory (DFT) calculations, it is found that the photocatalytic charge transfer pathway conforms to the Z-scheme mechanism, which not only greatly accelerates the separation and transfer of photogenerated charges, but also retains a high reduction capacity for water splitting. This work offers a good strategy for constructing highly efficient organic-inorganic heterojunctions for water splitting.
摘要：
光催化制氢的效率低主要是由于光吸收有限,电荷分离和水输送到活动中心。在这里，无机-有机Z方案异质结（CdS-COF-Ni）是通过在卟啉基共价有机框架上原位生长CdS纳米片，并在卟啉中心具有镍离子（COF-Ni）而构建的。在界面处形成一个内置电场，加速光生电荷的分离和转移。此外，通过在抗坏血酸（AC）溶液中的表面质子化处理，所得复合材料的亲水性明显提高,有利于水分子向光催化中心的迁移。在界面相互作用和表面质子化处理的协同作用下,在不添加任何助催化剂的情况下，光催化制氢速率优化为18.23mmolh-1g-1，是CdS的21倍。经过一系列的光电化学测量,原位X射线光电子能谱（XPS）分析，和密度泛函理论(DFT)计算，发现光催化电荷转移途径符合Z-方案机制，这不仅大大加速了光生电荷的分离和转移，而且还保留了很高的水分解还原能力。这项工作为构建高效的有机-无机异质结以进行水分解提供了良好的策略。
