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

Abstract

sluggish four electrons transfer process. [4] Two-dimensional (2D) materials present the advantages of a short exciton diffusion distance and a thickness less than the width of the space charge region at solid/liquid interfaces, thus potentially serve as the excellent photoanodes. [5,6] Indium sulfide (In 2 S 3) is a broad-spectral 2D material with ordered vacancy spinel-like structure, the sulfide anions are closely packed in layers, with octahedral-coordinated In cations present within the layers, and tetrahedralcoordinated In cations between them. [7,8] 2D In 2 S 3 is an n-type semiconductor with small size effect, exhibiting large surface area when its size is of nanometers, exposing a high percentage of edges that could produce active surface toward catalytic reaction. The variation of size in nanometer scale could also tune the bandgap based on quantum size and surface effect. [9,10] The common approaches to the fabrication of 2D In 2 S 3 include chemical vapor deposition, hydrothermal, solvothermal, and solgel process, however, precise controlling the dimensions of this compound is still difficult and have not been reported. [11,12] Fortunately, in a solvothermal reaction, the size and shape of the products could be controlled by nucleation and subsequent growth. The homogeneous nucleation limits the formation of nucleation sites and quantity attributing to the diversity of surface energy and nucleation barrier. [13] In 2 S 3 was fabricated by the former researchers usually leads to the large multilayer flakes, [8,14] whereas a lower surface energy can make it easier to grow on seed sites. Therefore, seed-mediated growth has a good control of nucleation density, and thus attaining uniform structure with desired edges. Introduction of alien atoms to 2D material is an effective way for tuning electrical and optical properties of the host material via orbital hybridization. [15] The Fermi level E F of most n-type semiconductors can be tuned by introducing impurity doping which is capable of causing dramatic changes in their interlayer electrical structure. [16-18] Once the position of hybridized impurity level is near the E F or valence band, it becomes the electrons or holes trap center (e.g., P-CdS and Gd-BiVO 4) and then affects the charge separation. [19-21] The doping pattern of the impurity species in the host materials include interstitial and substitutional sites. If an impurity atom is located in the gap between atoms in the lattice, it often refers to an interstitial doping, whereas an impurity atom substitute at the position of metal or chalcogen

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

“…The higher V ph (∼395 mV) for Fe 2 O 3 /NaYF 4 /Yb, Er manifests the E fp shifts downward, meaning that more photogenerated holes can migrate to the photoanode surface, resulting in a superior carrier transport kinetics (Figure S13c). , …”

“…The higher V ph (∼395 mV) for Fe 2 O 3 /NaYF 4 /Yb, Er manifests the E fp shifts downward, meaning that more photogenerated holes can migrate to the photoanode surface, resulting in a superior carrier transport kinetics (Figure S13c). 10,44 Additionally, the frequency-dependent controlled intensity modulated photocurrent spectrometer (CIMPS) response was employed to probe the carrier dynamics of Fe 2 O 3 /NaYF 4 /Yb, Er at the electrode/electrolyte interface. 10,45 The maximum phase shift was found at the vertex of the semicircle, corresponding to the rate constant f which represents the carrier transport dynamics.…”

“…10,44 Additionally, the frequency-dependent controlled intensity modulated photocurrent spectrometer (CIMPS) response was employed to probe the carrier dynamics of Fe 2 O 3 /NaYF 4 /Yb, Er at the electrode/electrolyte interface. 10,45 The maximum phase shift was found at the vertex of the semicircle, corresponding to the rate constant f which represents the carrier transport dynamics. The higher value f indicates faster carriers' migration and rare carriers' recombination.…”

“…Besides, the small-size In 2 S 3 nanosheets displayed an increased photon absorption by tailoring their electronic structure. Attributed to the P doping, the photoabsorption edge of In 2 S 3 nanosheets was extended from 400 to 550 nm by the hybridization of P 3s, P 3p, and S 3p orbitals . Furthermore, the TiO 2 @Si/Fe/rGO film exhibited enhanced photoabsorption compared to pristine TiO 2 owing to the reduced charge recombination by rGO .…”

“…Attributed to the P doping, the photoabsorption edge of In 2 S 3 nanosheets was extended from 400 to 550 nm by the hybridization of P 3s, P 3p, and S 3p orbitals. 10 Furthermore, the TiO 2 @Si/Fe/rGO film exhibited enhanced photoabsorption compared to pristine TiO 2 owing to the reduced charge recombination by rGO. 11 Although the above strategies have realized red-shifting of the photon absorption, using infrared light in PEC water splitting is still a challenging task.…”