Morphology-controlled perovskite/α-Fe2O3 heterojunctions for solar energy conversion of CO2
Shou-Heng Liu a
a Department of Environmental Engineering, National Cheng Kung University
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP23)
Kobe, Japan, 2023 January 22nd - 24th
Organizers: Seigo Ito, Hideo Ohkita and Atsushi Wakamiya
Poster, Shou-Heng Liu, 064
Publication date: 21st November 2022

A new monoclinic-rich CsPbBr3/porous α-Fe2O3 with 3D/3D heterojunction has been prepared by a facile one-step ligand-assisted reprecipitation (LARP) under low temperature and air atmosphere. The morphologies (i.e., cubic and monoclinic phases) of CsPbBr3 are easily tuned by varying the ratios of precursor solution during the LARP process. Upon the heterojunction of monoclinic-rich CsPbBr3 with porous α-Fe2O3, the electron consumption rate is further enhanced to 3.38 mmol g-1 h-1, which is ca. 2.4-fold improvements of pristine monoclinic-rich CsPbBr3. The surpassing performance could be attributed to the higher CO2 uptakes, superior charge separation and H2O photooxidation via the photoinduced holes in the valence band of α-Fe2O3. The XRD patterns of CsPbBr3 (denoted as CPB-1), α-Fe2O3 (denoted as Fe2O3) and CsPbBr3/α-Fe2O3 (denoted as CPB/Fe2O3-y) can be seen in Figure 1. The co-existence of monoclinic (JPCDs 18-0364) phases of CsPbBr3 together with α-Fe2O3 (JPCDs 33-0664) implies the successful synthesis of CPB/Fe2O3-y. A possible charge separation and transfer mechanism of CPB/Fe2O3-3 composite can be proposed as shown in Figure 2. The EF of CsPbBr3 (-5.39 eV vs. vacuum) is higher than that of α-Fe2O3 (-5.57 eV vs. vacuum), resulting in free electron transfer from CsPbBr3 to α-Fe2O3 until the equilibrium of their EF upon the intimate contact of CsPbBr3 and α-Fe2O3. As such, the creation of built-in electric field together with the band edge bending would be occurred at the interface of CPB/Fe2O3-3. Due to the alignment of EF and band bending at the interface of CsPbBr3/α-Fe2O3, the photogenerated electrons in the CB of α-Fe2O3 (downward band bending) would recombine with photoinduced holes in the VB of CsPbBr3 (upward band bending) via non-radiative recombination at the interface, forming the direct Z-scheme charge transfer pathway. Consequently, the photoexcited electrons in the CB of CsPbBr3 possess higher potential to perform the photoreductions, including CO2-to-CO, CO2-to-CH4 and H+-to-H2. At the same time, the photooxidation of H2O can be occurred by the holes on the VB of α-Fe2O3. The Z-scheme charge transfer mechanism of CsPbBr3/α-Fe2O3 composite not only exhibit the superior photoactivity in CO2 photoreduction but also enhance the chemical stability of CsPbBr3, which demonstrated the great potential in the photoelectric applications.

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