Self‐Assembled BiFeO₃‐ε‐Fe₂O₃ Vertical Heteroepitaxy for Visible Light Photoelectrochemistry

Abstract

Self‐assembled vertical heterostructure with a high interface‐to‐volume ratio offers tremendous opportunities to realize intriguing properties and advanced modulation of functionalities. Here, a heterostructure composed of two visible‐light photocatalysts, BiFeO3 (BFO) and ε‐Fe2O3 (ε‐FO), is designed to investigate its photoelectrochemical performance. The structural characterization of the BFO‐FO heterostructures confirms the phase separation with BFO nanopillars embedded in the ε‐FO matrix. The investigation of band structure of the heterojunction suggests the assistance of photoexcited carrier separation, leading to an enhanced photoelectrochemical performance. The insights into the charge separation are further revealed by means of ultrafast dynamics and electrochemical impedance spectroscopies. This work shows a delicate design of the self‐assembled vertical heteroepitaxy by taking advantage of the intimate contact between two phases that can lead to a tunable charge interaction, providing a new configuration for the optimization of photoelectrochemical cell.

Metal Oxide Nanocomposites: A Perspective from Strain, Defect, and Interface

“…Enhancement of photo‐electrochemical solar water oxidation was also observed in quite a few of other systems. Chu and co‐workers have investigated photocatalysts in BFO:ε‐Fe 2 O 3 VANs by investigating the band structure, ultrafast time‐resolved spectroscopy and electrochemical impedance spectroscopy . It was found the VAN structure assists photoexcited carrier separation and suppresses electron–hole recombination, giving rise to enhanced photo‐electrochemical performance in this VAN system as well as in the NiWO 4 :WO 3 VAN system .…”

Photoelectrochemical Device Designs toward Practical Solar Water Splitting: A Review on the Recent Progress of BiVO4 and BiFeO3 Photoanodes

“…As a result of such efforts, a few candidates have been introduced and investigated extensively. The promising candidates are BiVO 4 [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], Fe 2 O 3 [25][26][27][28][29][30][31][32], and BiFeO 3 [33][34][35]. Figure 2 shows the band gap energies and band edge positions of various semiconductors with respect to the water redox potential.…”

“…The realization of such device designs is challenging, especially since it requires carefully controlled material growth techniques to expose favorably oriented crystal facets on the surface. Moreover, the application of ferroelectric into the PEC water splitting requires rigid and stable ferroelectric performance, with properties that can be made through elaborate fabrication methods, such as vacuum deposition of pulsed laser deposition (PLD) [33,35]. As a physical vapor deposition technique, PLD is well-known, as its advantages for its deposition of pure and highly crystalline thin film [50,51].…”

Magnetic properties of ε iron(III) oxide nanorod arrays functionalized with gold and copper(II) oxide

“…Nanomaterials based on iron(III) oxides, eventually functionalized with metal or metaloxide nanoparticles (NPs), are attractive platforms for various technological applications, encompassing biomedicine, (photo)catalysis, solar assisted H2 generation, gas sensing/batter ies, and magnetic devices [1][2][3][4][5][6][7]. To this regard, due to the search for iron oxide-based nanomateria ls endowed with specific features, the scarcely investigated ferrimagnetic -Fe2O3 polymorph has emerged for its peculiar properties with respect to the most stable and widely studied -Fe2O3 and -Fe2O3 [8][9][10][11][12].…”

“…To this regard, due to the search for iron oxide-based nanomateria ls endowed with specific features, the scarcely investigated ferrimagnetic -Fe2O3 polymorph has emerged for its peculiar properties with respect to the most stable and widely studied -Fe2O3 and -Fe2O3 [8][9][10][11][12]. Indeed, -Fe2O3 nanomaterials diplay a superior activity in solar-assisted photocatalytic process [2][3][13][14] and intriguing magnetic properties, such as giant roomtemperature coercive field, that can be exploited for the fabrication of electric/magnetic field or multiple-state memory devices [1,[15][16][17][18]. In this context, a considerable attention has been devoted to the possibility of boosting material performances by suitable surface functionalizatio n, that represents a strategic option for the development of multi-functional systems to be exploited in various tecnological applications [4].…”