Band Edge Engineering of BiOX/CuFe₂O₄ Heterostructures for Efficient Water Splitting

Abstract

Layered bismuth oxyhalides (BiOX, X = Cl, Br, and I) are promising visible light-responsive photocatalysts but suffer from inadequate electron transportation from the bulk to the surface. Construction of heterostructures has been considered as a convenient approach to improve the spatial charge carrier separation and enhance the efficiencies of the surface-reactive charges for catalysis. Here, a series of heterostructures has been successfully designed for n-type bismuth oxyhalides and p-type spinel ferrites CuFe2O4 (CFO) by a facile and generalized protocol via the hydrothermal method followed by the co-precipitation method. The heterostructure introduces built-in electric field at the interface that facilitates vectorial charge transfer, which demonstrated significantly improved visible light-driven photocatalytic activity toward H2 generation without using any noble metal co-catalyst. A conventional type-I and type-II charge transfer mechanism has been followed for BiOBr/CFO and BiOI/CFO heterostructures, respectively, which may effectively lower charge transfer resistance compared to that for bare BiOBr and BiOI, suggesting facile charge transfer. Remarkably, a direct Z-scheme BiOCl/CFO heterostructure has been formed between BiOCl and CFO with an intimate interfacial contact, which demonstrated 5.7 times higher H2 generation activity than pure BiOCl and two fold improved catalytic efficiency compared to type-II BiOI/CFO heterostructures under visible light. Very low resistance in electrochemical impedance spectra confirmed the superiority of the direct Z-scheme in promoting the charge separation and transfer and increase in carrier density. Moreover, the optimal space charge layer width and the redox potentials have been achieved for BiOCl/CFO through the engineering of band edge potentials, which reduces the fast recombination rate. This work offers a paradigm for the design of highly engineered BiOX-based heterostructures with tuned band structures for efficient photocatalytic water splitting.

Synthesis and Structure of the Double-Layered Sillén–Aurivillius Perovskite Oxychloride La2.1Bi2.9Ti2O11Cl as a Potential Photocatalyst for Stable Visible Light Solar Water Splitting

“…Using 0.1 M Na 2 SO 4 (pH = 2.26) as an electrolyte, La 2.1 Bi 2.9 Ti 2 O 11 Cl synthesized at 820 °C for 20 h resulted in a photocurrent density of about 15 μA cm –2 (Figure S10), while all other tested synthesis condition combinations (20 h at 780 °C, and 800 °C and 5 and 10 h at 820 °C) resulted in compounds with lower photoelectrochemical activity. The photocurrent density is relatively stable compared to other visible light-driven photoelectrodes based on mixed anion materials, which show considerable decline after several seconds up to a few minutes. − The stability of La 2.1 Bi 2.9 Ti 2 O 11 Cl is likely to originate from its band structure. In contrast to oxynitrides, oxysulfides, and oxyhalides where the VBE is composed mainly of the non-oxide anion p orbitals (e.g., N 2p or Cl 3p), the VBE of this material is dominated by O 2p orbitals as discussed prior.…”

Phosphorus based hybrid materials for green fuel generation

“…The formation of the type‐I straddling gap in the heterostructure and the band edge positions as well as the band gap of the BAs–BlueP heterostructure are located at energetically favorable positions to split water at pH = 0. Conceptually, the direct Z type heterostructure can form a more negative potential of the CBM and more positive potential of the VBM with a strong reduction and oxidation ability compared with the traditional type II heterostructure (Bera et al, 2022). For example, Lang and Hu (Lang et al, 2020) evaluated the structural and electronic properties of the 2D vdW BlueP/PN heterojunction as a potential Z‐scheme photocatalysts for water splitting using DFT calculations.…”

Fast and Facile Microwave Synthesis of Cubic CuFe2O4 Nanoparticles for Electrochemical CO2 Reduction

“…CuFe 2 O 4 has been used for several catalytic processes, such as methanol steam reforming, [ 22 ] photocatalytic degradation, [ 23 ] photocatalytic water splitting, [ 25 ] photoelectrochemical hydrogen evolution, [ 26 ] photoelectrochemical water oxidation, [ 27,28 ] as well as gas sensor material [ 29 ] or for protein separation. [ 30 ] A huge advantage is the easy recovery of the material due to its magnetic properties.…”

“…[19,24] This has experimentally been observed by a reduced grain resistance and improved conductivity for partially inverse tetragonal CuFe 2 O 4 compared to normal cubic CuFe 2 O 4 . [19] CuFe 2 O 4 has been used for several catalytic processes, such as methanol steam reforming, [22] photocatalytic degradation, [23] photocatalytic water splitting, [25] photoelectrochemical hydrogen evolution, [26] photoelectrochemical water oxidation, [27,28] as well as gas sensor material [29] or for protein separation. [30] A huge advantage is the easy recovery of the material due to its magnetic properties.…”