Conjugated π Electrons of MOFs Drive Charge Separation at Heterostructures Interface for Enhanced Photoelectrochemical Water Oxidation

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2021-04, Vol.17 (14), p.e2100367-n/a
• Main Authors: Wang, Xuewei, Sun, Wenming, Tian, Yang, Dang, Kun, Zhang, Qimeng, Shen, Zhurui, Zhan, Sihui
• Format: Article
• Language: English
• Subjects: Charge efficiency; charge separation; Charge transfer; Clean energy; Conjugation; Electric fields; Electrolytes; Electronegativity; Electrons; heterojunction; Heterojunctions; Heterostructures; metal organic framework; Metal-organic frameworks; Nanorods; Nanotechnology; Oxidation; photoanode; Photoelectric effect; Photoelectric emission; Separation; Titanium dioxide; water oxidation; Water splitting
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202100367

Photoanode material with high efficiency and stability is extensively desirable in photoelectrochemical (PEC) water splitting for green/renewable energy source. Herein, novel heterostructures is constructed via coating rutile TiO2 nanorods with metal organic framework (MOF) materials UiO‐66 or UiO‐67 (UiO‐66@TiO2 and UiO‐67@TiO2), respectively. The π electrons in the MOF linkers could increase the local electronegativity near the heterojunction interface due to the conjugation effect, thereby enhancing the internal electric field (IEF) at the heterojunction interface. The IEF could drive charge transfer following Z‐scheme mechanism in the prepared heterostructures, inducing photogenerated charge separation efficiency increasing as 156% and 253% for the UiO‐66@TiO2 and UiO‐67@TiO2, respectively. Correspondingly, the UiO‐66@TiO2 and UiO‐67@TiO2 enhanced the photocurrent density as approximate two‐ and threefolds compared with that of pristine TiO2 for PEC water oxidation in universal pH electrolytes. This work demonstrates an effective method of regulating the IEF of heterojunction toward further improved charge separation. The heterojunctions of UiO‐MOF shell coating TiO2 nanorod surface are promising as photoanode in photoelectrochemical cells to enhance photocurrent density. The conjugated π electrons in UiO‐67 shell are able to strengthen the intensity of interfacial electric field. The charge transfer at heterojunction interface thereby follows Z‐scheme, promoting the electron–hole separation during photoelectrochemical water oxidation.