Manipulation of Charge Transfer in FeP@Fe₂O₃ Core–Shell Photoanode by Directed Built-In Electric Field

Abstract

Hematite (Fe2O3) can be suitable when used in a solar energy conversion system, but the short charge diffusion lengths limit its applications. Here, we report the studies of charge transfer ability with a 40 nm Fe2O3 nanorod decorated by a 5 nm iron phosphide (FeP) core–shell structure. By selecting the optimized time of phosphorization (20 min), the photocurrent of FeP@Fe2O3-20 photoanode reached 0.86 mA/cm2, enhanced by 4.10-fold compared with pristine Fe2O3 (0.21 mA/cm2) for water oxidation. Further, the charge transport time reduced by 30% due to the FeP shell that served as the hole transport layer. Compared with Fe2O3, FeP@Fe2O3 has a higher Fermi level, which guides the electron’s transfer from FeP to Fe2O3 to create a space charge layer. The charge balance induces an upward bending of band structure at the FeP and Fe2O3 interface and accelerates the separation of photogenerated electron–holes ascribed to the built-in electric field at the interface. Our studies provide a detailed understanding of carrier dynamics in the core–shell structure, demonstrating a new route to explore high efficiency approaches for solar harvesting.

Hematite Photoanodes for Solar Water Splitting: A Detailed Spectroelectrochemical Analysis on the pH-Dependent Performance

“…Hematite (α-Fe 2 O 3 ) has been extensively explored as a photoanode for water oxidation leveraging its relatively narrow band gap energy (1.9–2.2 eV), robustness, and low-cost fabrication using solution-processable routes. , A wide range of bulk and surface engineering treatments involving doping, , nanostructuring, , surface reconstruction, and electrocatalyst deposition, , among others, have shown great promise at overcoming the relatively poor performance of hematite photoanodes either by improving bulk electronic features or by conditioning the semiconductor–liquid junction (SCLJ) characteristics (reducing surface states, adjusting energy bands, enhancing catalytic activities). Alternatively, the electrolyte composition also plays an active role on the PEC response, not only by modulating ion transport but also by directly affecting the interfacial characteristics of the photoanode. , For instance, it has been reported that changes of the local pH can alter the relative alignment between the semiconductor energy bands and the water redox energy levels, modify the reaction mechanism, , or even change the surface chemistry .…”

Manipulating the Low-Energy Photons by an Upconversion Fluorescent Hybrid Photocatalyst for Water Oxidation

“…X-ray diffraction (XRD) was employed to analyze these semiconductors’ crystal structures . The XRD patterns demonstrated the tetragonal anatase TiO 2 (JCPDS 99-0008), cubic In 2 O 3 (JCPDS 71-2194), , orthorhombic Ta 2 O 5 (JCPDS 79-1375), and rhombohedral Fe 2 O 3 (JCPDS 85-0987) (Figure a) . X-ray photoelectron spectroscopy (XPS) identified the surface chemical state of TiO 2 , Ta 2 O 5 , and Fe 2 O 3 , indicating that our prepared semiconductors are pure (without any second phases) (Figure S3).…”

Tuning Electronic Structure of 2D In2S3 via P Doping and Size Controlling Toward Efficient Photoelectrochemical Water Oxidation

“…The hybridized state by P doping could behave as the charge traps to suppress charge recombination because the electrons in the traps will take a long time for exciting to conduction band, resulting in an efficient charge separation. [38] Figure 5f shows the spectra of time-resolved transient PL (TRPL) decay, the plot on semiology scale shows the third-order exponential decay (Table S3, Supporting Information). [20,39] The fitted time profiles imply the P-In 2 S 3 (s) has a longer decay time (681.1 ps) than In 2 S 3 (s) (665.9 ps), proving the impurity states are effective in prolonging the lifetime of photogenerated electrons hence facilitating the charge transport from the conduction band of P-In 2 S 3 (s) to FTO substrate.…”