Simultaneous Enhancement of Charge Separation and Hole Transportation in a W:α-Fe₂O₃/MoS₂ Photoanode: A Collaborative Approach of MoS₂ as a Heterojunction and W as a Metal Dopant

Abstract

In this study, a facile approach has been successfully applied to synthesize a W-doped Fe 2 O 3 /MoS 2 core−shell electrode with unique nanostructure modifications for photoelectrochemical performance. A two-dimensional (2D) structure of molybdenum disulfide (MoS 2 ) and tungsten (W)-doped hematite (W:α-Fe 2 O 3 ) overcomes the drawbacks of the α-Fe 2 O 3 and MoS 2 semiconductor through simple and facile processes to improve the photoelectrochemical (PEC) performance. The highest photocurrent density of the 0.5W:α-Fe 2 O 3 /MoS 2 photoanode is 1.83 mA•cm −2 at 1.23 V vs reversible hydrogen electrode (RHE) under 100 mW•cm 2 illumination, which is higher than those of 0.5W:α-Fe 2 O 3 and pure α-Fe 2 O 3 electrodes. The overall water splitting was evaluated by measuring the H 2 and O 2 evolution, which after 2 h of irradiation for 0.5W:α-Fe 2 O 3 /MoS 2 was determined to be 49 and 23.8 μmol.cm −2 , respectively. The optimized combination of the heterojunction and metal doping on pure α-Fe 2 O 3 (0.5W:α-Fe 2 O 3 /MoS 2 photoanode) showed an incident photon-to-electron conversion efficiency (IPCE) of 37% and an applied bias photon-to-current efficiency (ABPE) of 26%, which are around 5.2 and 13 times higher than those of 0.5W:α-Fe 2 O 3 , respectively. Moreover, the facile fabrication strategy can be easily extended to design other oxide/carbon-sulfide/oxide core−shell materials for extensive applications.

An efficient strategy to boost the directed migration of photogenerated holes by introducing phthalocyanine as a hole extraction layer

“…S2(b)†) displays a high peak at 529.9 eV corresponding to lattice oxygen (O 2− ) and a low peak at 531.6 eV corresponding to surface-absorbed hydroxyl groups (OH − ) on the surface of Ti-Fe 2 O 3 . 17 Fig. S2(c)† shows the Ti 2p XPS spectrum with two peaks at 458.0 eV and 464.4 eV, demonstrating the presence of Ti 4+ in Ti-Fe 2 O 3 .…”

“…S2(b) †) displays a high peak at 529.9 eV corresponding to lattice oxygen (O 2− ) and a low peak at 531.6 eV corresponding to surface-absorbed hydroxyl groups (OH − ) on the surface of Ti-Fe 2 O 3 . 17 Ti 4+ in Ti-Fe 2 O 3 . 18,19 As such, Ti-Fe 2 O 3 is successfully fabricated.…”

“…Evidently, a further enhancement of the OCPV value could be discovered from CoPi/Ti-Fe 2 O 3 to CoPi/Pc/Ti-Fe 2 O 3 , confirming the superior separation efficiency of CoPi/Pc/Ti-Fe 2 O 3 . 15,17 Finally, the oriented charge transfer in the bulk CoPi/Pc/Ti-Fe 2 O 3 was probed by the lifetime of photogenerated holes. According to the reported literature, the interfacial electric field motivates photogenerated charge separation in the bulk photoanode upon exposure to light, conversely, the recombination of photogenerated holes with electrons would be speeded up by the interfacial electric field when light is turned off.…”

Efficient and Stable MoOX@Mo-BiVO4 Photoanodes for Photoelectrochemical Water Oxidation: Optimization and Understanding

“…As depicted in Figure d, Mo doping and MoO X formation at the MoO X @2% Mo-BiVO 4 photoanode indicate a relatively high IPCE value (17.7%), which is 3.7 times higher when compared with the pure BiVO 4 photoanode (4.8%). The PEC performance of an electrode is evaluated based on its light absorption efficiency, electron–hole separation, and charge carrier migration. , Therefore, the improved PEC performance can be ascribed to the higher charge transfer, and separation efficiencies resulted from the formation of MoOx, which is beneficial for the suppression of the electron hole recombination. This result was found to be reliable based on the enhancements observed in the photocurrent density (Figure a).…”

Synergy Promotion of Elemental Doping and Oxygen Vacancies in Fe2O3 Nanorods for Photoelectrochemical Water Splitting

“…Theoretical calculations and experimental results demonstrated that extrinsic elemental doping is an effective approach to increase the conductivity, lifetime of charge carriers, and hole diffusion length by delocalization of the Fe 3d orbit on the bottom of the conduction band of α-Fe 2 O 3 . − Especially, doping of extrinsic elements can increase the charge density of Fe and O atoms at neighboring sites and thus promote the charge separation efficiency and introduce active sites for water oxidation, which can improve the PEC water splitting performance of α-Fe 2 O 3 effectively. , Wang et al found that Ti doping can act as an electron donor and increase the charge density in α-Fe 2 O 3 NRs, and the photocurrent density increased from 1 mA·cm –2 to 2.8 mA·cm –2 at 1.23 V versus the RHE . Luo et al fabricated P-doped Fe 2 O 3 with a photocurrent density of 1.48 mA·cm –2 at 1.23 V versus the RHE, and this excellent performance was attributed to the band bending caused by P doping …”