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Enhanced Photoelectrochemical Water Oxidation Using TiO₂-Co₃O₄ p-n Heterostructures Derived from in Situ-Loaded ZIF-67.

ABSTRACT: Exposing catalytically active metal sites in metal-organic frameworks (MOFs) while maintaining porosity is beneficial for increasing electron transport to achieve better electrochemical energy conversion performance. Herein, we propose an in situ method for MOF formation and loading onto TiO₂ nanorods (NR) using a simple solution-processable method followed by annealing to obtain TiO₂-Co₃O₄. The as-prepared TiO₂-ZIF-67 based photoanodes were annealed at 350, 450, and 550 °C to study the effect of carbonization on photo-electrochemical water oxidation. The successful loading of ZIF-67 on TiO₂ and the formation of TiO₂-Co₃O₄ heterojunction were confirmed by XRD, XPS, FE-SEM, and HRTEM analyses. TiO₂-Co₃O₄-450 (the sample annealed at 450 °C) showed an enhanced photocurrent of 2.4 mA/cm², which was 2.6 times larger than that of pristine TiO₂. The improved photocurrent might be ascribed to the prepared p-n heterostructures (Co₃O₄ and TiO₂), which promote electron-hole separation and charge transfer within the system and improve the photoelectrochemical performance. Moreover, the preparation of Co₃O₄ from the MOF carbonization process improved the electrical conductivity and significantly increased the number of exposed active sites and enhanced the photoresponse performance. The as-prepared ZIF-67 derived TiO₂-Co₃O₄ based photoanodes demonstrate high PEC water oxidation, and the controlled carbonization method paves the way toward the synthesis of low-cost and efficient electrocatalysts.

SUBMITTER: Thanh Thu CT

PROVIDER: S-EPMC10420101 | biostudies-literature | 2023 Aug

REPOSITORIES: biostudies-literature

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Publications

Enhanced Photoelectrochemical Water Oxidation Using TiO2-Co3O4 p-n Heterostructures Derived from in Situ-Loaded ZIF-67.

Thanh Thu Chau Thi CT Jo Hyo Jeong HJ Koyyada Ganesh G Kim Dae-Hwan DH Kim Jae Hong JH

Materials (Basel, Switzerland) 20230804 15

Exposing catalytically active metal sites in metal-organic frameworks (MOFs) while maintaining porosity is beneficial for increasing electron transport to achieve better electrochemical energy conversion performance. Herein, we propose an in situ method for MOF formation and loading onto TiO2 nanorods (NR) using a simple solution-processable method followed by annealing to obtain TiO2-Co3O4. The as-prepared TiO2-ZIF-67 based photoanodes were ...[more]

PMID: 37570165

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Project description:Semiconductor heterostructure junctions are known to improve the water oxidation performance in photoelectrochemical (PEC) cells. Depending on the semiconductor materials involved, different kinds of junctions can appear, for instance, type II band alignment where the conduction and valence bands of the semiconductor materials are staggered with respect to each other. This band alignment allows for a charge separation of the photogenerated electron-hole pairs, where the holes will go from low-to-high valance band levels and vice versa for the electrons. For this reason, interface engineering has attracted intensive attention in recent years. In this work, a simplified model of the Fe2O3-TiO2 heterostructure was investigated via first-principles calculations. The results show that Fe2O3-TiO2 produces a type I band alignment in the heterojunction, which is detrimental to the water oxidation reaction. However, the results also show that interstitial hydrogens are energetically allowed in TiO2 and that they introduce states above the valance band, which can assist in the transfer of holes through the TiO2 layer. In response, well-defined planar Fe2O3-TiO2 heterostructures were manufactured, and measurements confirm the formation of a type I band alignment in the case of Fe2O3-TiO2, with very low photocurrent density as a result. However, once TiO2 was subjected to hydrogen treatment, there was a nine times higher photocurrent density at 1.50 V vs. the reversible hydrogen electrode under 1 sun illumination as compared to the original heterostructured photoanode. Via optical absorption, XPS analysis, and (photo)electrochemical measurements, it is clear that hydrogen treated TiO2 results in a type II band alignment in the Fe2O3-H:TiO2 heterostructure. This work is an example of how hydrogen doping in TiO2 can tailor the band alignment in TiO2-Fe2O3 heterostructures. As such, it provides valuable insights for the further development of similar material combinations.

Dataset Information

Enhanced Photoelectrochemical Water Oxidation Using TiO₂-Co₃O₄ p-n Heterostructures Derived from in Situ-Loaded ZIF-67.

Publications

Enhanced Photoelectrochemical Water Oxidation Using TiO<sub>2</sub>-Co<sub>3</sub>O<sub>4</sub> p-n Heterostructures Derived from in Situ-Loaded ZIF-67.

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