Covalent SO Bonding Enables Enhanced Photoelectrochemical Performance of Cu₂S/Fe₂O₃ Heterojunction for Water Splitting

Abstract

O 3 ), possessing a bandgap of 1.9-2.2 eV and theoretically enabling a photocurrent density of 12.6 mA cm −2 at 1.23 V versus reversible hydrogen electrode (RHE) for water splitting, [6] become one of the most investigated photoanode materials. Additionally, Hematite has stable properties, abundant reserves, and nontoxicity compared with other photoanode materials. [7] However, the photoelectrochemical performance of hematite is severely restricted by its short hole diffusion length (≈2-4 nm), low conductivity, and short lifetime of the excited state carriers (≈10 −12 s). Furthermore, a high concentration of surface states and slow kinetics for sluggish oxygen evolution reaction (OER) at the surface of Fe 2 O 3 call for the necessary modifications to improve the PEC performance.Cu 2 S, a p-type semiconductor with a narrow bandgap (1.2 eV), is attracting broad interest for solar energy conversion and storage in numerous applications. [8][9][10] It is ideally suitable for harvesting sunlight in a wide wavelength range and simultaneously the high conductivity allows for efficient photogenerated charge transfer. Moreover, copper vacancies are generated once copper(I) sulfide is exposed to oxygen, and then an localized surface plasmon resonance band will emerge. [11,12] This property of copper sulfide enables the utilization of sunlight with the wavelength up to the near-infrared region. Due to the photothermal effect, CuS compound nanocrystals have been used widely for energy storage and photothermal therapy. [13,14] Importantly, a recent report demonstrates that the derivatives of Cu 2 S under the condition of OER The severe charge recombination and the sluggish kinetic for oxygen evolution reaction have largely limited the application of hematite (α-Fe 2 O 3 ) for water splitting. Herein, the construction of Cu 2 S/Fe 2 O 3 heterojunction and discover that the formation of covalent SO bonds between Cu 2 S and Fe 2 O 3 can significantly improve the photoelectrochemical performance and stability for water splitting is reported. Compared with bare Fe 2 O 3 , the heterostructure of Cu 2 S/Fe 2 O 3 endows the resulting electrode with enhanced charge separation and transfer, extended range for light absorption, and reduced charge recombination rate. Additionally, due to the photothermal properties of Cu 2 S, the heterostructure exhibits locally a higher temperature under illumination, profitable for increasing the rate of oxygen evolution reaction. Consequently, the photocurrent density of the heterostructure is enhanced by 177% to be 1.19 mA cm −2 at 1.23 V versus reversible hydrogen electrode. This work may provide guideline for future in the design and fabrication of highly efficient photoelectrodes for various reactions.

Mono-Doped and Co-Doped Nanostructured Hematite for Improved Photoelectrochemical Water Splitting

“…where J p is the photocurrent density (mAcm −2 ), V bias is the applied voltage between the two electrodes and P in is the incident illumination power density (100 mWcm −2 ). Figure 8 presents the calculated ABPE efficiency of pristine and doped hematite for a bias potential of 0.2-1.2 V vs. RHE [31][32][33]. It can be seen that the efficiency increased as the potentials were increased for the doped samples.…”

Recent Progress on Semiconductor Heterojunction‐Based Photoanodes for Photoelectrochemical Water Splitting

“…As the frequency of infrared rays is close to the frequency of the material, it is easier to cause resonance of the material, and the thermal effect is significant. For example, Zhang et al [ 129 ] used the photothermal effect of Cu 2 S to enhance the light absorption of visible light and near‐infrared (NIR) light radiation and to profitably increase the rate of OER due to the in situ heating of Cu 2 S.…”

“…As the frequency of infrared rays is close to the frequency of the material, it is easier to cause resonance of the material, and the thermal effect is significant. For example, Zhang et al [129] used the photothermal effect of Cu 2 S to enhance the light absorption of visible light and near-infrared (NIR) light radiation and to profitably increase the rate of OER due to the in situ heating of Cu 2 S. Generally, there are a number of photothermal materials: organic composites, noble metals, carbon-based materials, and transition metal semiconductors. The photothermal effect is mostly based on the principle of surface plasmon resonance.…”

Piezotronic Effect-Assisted Photoelectrochemical Exosomal MicroRNA Monitoring Based on an Electron Donor Self-Supplying Strategy

“…Several distinct peaks located at 28.30, 32.80, 47.07, 55.90, 58.59, and 68.71°were ascribed to the (113), ( 200), ( 220), (133), and (226) crystal planes of tetragonal Bi 2 WO 6 (JCPDS #39-0256). 34 After the incorporation of Cu 2 S, several new diffraction peaks at 32.5, 46.5, and 54.5°which can be referred to the tetragonal structure of Cu 2 S (JCPDS #84-0209) appeared, 29 indicating the successful fabrication of Bi 2 WO 6 /CuS 2 composites. The low diffraction peak intensity of Cu 2 S was plausibly attributed to its ultrasmall size and low content compared to Bi 2 WO 6 .…”

“…17 Narrow band gap (∼1.2 eV) Cu 2 S with a proper band gap and high absorption coefficient was selected to construct heterostructures with Bi 2 WO 6 , guaranteeing efficient light absorption and utilization. 29,30 Therefore, desirable PEC performance would be anticipated within heterostructured Bi 2 WO 6 /CuS 2 based on the synergistic effects from their hybrids.…”