In-Plane Axially Enhanced Photocatalysis by Re₄ Diamond Chains in Layered ReS₂

Two-dimensional (2D) semiconductors play a crucial role in high-efficiency photocatalysts because of their high surface-to-volume ratio. The surface property is a key part of photocatalysis. In this work, the enhanced photocatalytic behavior of the layered ReS₂ with optical polarization along the Re₄ nano-diamond-chain (DC) direction (b axis) has been demonstrated. The unpolarized photoconductivity (PC) response of ReS₂ with an applied bias along the b axis is approximately 1 order higher than that of the applied bias perpendicular to the b axis. The polarization-dependent PC spectra of E ∥ b also reveal a higher photoresponsivity with respect to those measured along the E ⊥ b polarization for the layered ReS₂. This result indicates that stronger polarization dipoles as well as a larger amount of photogenerated carriers and surface states can contribute to the C-plane ReS₂ under the illumination of E ∥ b polarized photons. With the special axial effect, the layered ReS₂ 2D photocatalyst shows much faster degradation rates of 5.6 and 12.3 than the other transition-metal dichalcogenides of TaS₂ and MoS₂ for the degradation of methylene blue (MNB) solution. For the polarization-dependent photodegradation test, the degradation rate of illuminated E ∥ b polarized photons is also approximately 12 times faster than that of the illuminated E ⊥ b polarized light in a 25 μM MNB solution. The enhanced photocatalytic behavior of ReS₂ along the DC also shows a peak photoreponse of ∼25 μV detected in the polarized photovoltaic spectrum of the 0.5 μM MNB dye-sensitized solar cell positioned at ∼1.99 eV. The formation of a nano-DC and a one-layer trigonal crystalline phase is beneficial for the versatile energy applications of ReS₂.