Modulating Charge Transfer Efficiency of Hematite Photoanode with Hybrid Dual‐Metal–Organic Frameworks for Boosting Photoelectrochemical Water Oxidation

• Published in: Advanced science 2020-12, Vol.7 (23), p.2002563-n/a
• Main Authors: Wang, Keke, Liu, Yang, Kawashima, Kenta, Yang, Xuetao, Yin, Xiang, Zhan, Faqi, Liu, Min, Qiu, Xiaoqing, Li, Wenzhang, Mullins, Charles Buddie, Li, Jie
• Format: Article
• Language: English
• Subjects: charge transfer efficiency; Efficiency; hematite; hybrid dual‐metal–organic frameworks; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; MATERIALS SCIENCE; Morphology; Oxidation; Semiconductors; water oxidation
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.202002563

The glorious charge transfer efficiency of photoanode is an important factor for efficient photoelectrochemical (PEC) water oxidation. However, it is often limited by slow kinetics of oxygen evolution reaction. Herein, a dual transition metal‐based metal–organic frameworks (MOF) cocatalyst, Fe@Ni–MOF, is introduced into a titanium‐doped hematite (Fe2O3:Ti) photoanode. The combination of Ni and Fe can optimize the filling of 3d orbitals. Moreover, the introduction of Fe donates electrons to Ni in the MOF structure, thus, suppressing the irreversible (long‐life‐time) oxidation of Ni2+ into Ni3+. The resulting Fe@Ni–MOF/Fe2O3:Ti photoanode exhibits ∼threefold enhancement in the photocurrent density at 1.23 V versus the reversible hydrogen electrode. Kinetic analysis of the PEC water oxidation processes indicates that this performance improvement is primarily due to modulating the charge transfer efficiency of hematite photoanode. Further results show that a single transition metal‐based MOF cocatalyst, Ni–MOF, exhibits slow charge transfer in spite of a reduction in surface charge recombination, resulting in a smaller charge transfer efficiency. These findings provide new insights for the development of photoelectrodes decorated with MOFs. Herein, a hybrid transition metal‐based metal–organic framework (MOF) cocatalyst (Fe@Ni–MOF) is loaded on the surface of a titanium‐doped hematite (Fe2O3:Ti) photoanode. The introduction of Fe optimizes the filling of 3d orbitals, donating electrons to Ni in the MOF structure. Thus thephotogenerated holes can be transferred to the surface of photoanode more efficiently, which will oxidize water instead of Ni2+.