Engineering the Interface of Cu/MoS2 Nanostructures for Improved Charge Transfer for Applications as PEC Anode Materials

Abstract

Electronic structures of metal and semiconductor composites play a crucial role in photoelectric conversion. To obtain a fast-response photoelectrochemical (PEC) anode, its orbital regulation is a challenge. Herein, the occupancy state of the d orbitals of Mo is adjusted to achieve high-efficiency photoelectric conversion by adjusting the quantity of Cu by magnetron sputtering deposited in Cu/MoS2 composites. Characterization results indicate that the SEM morphology of MoS2 changes distinctly. Meanwhile, the (111) and (200) diffraction peaks and 0 and 2+ valence states of Cu appeared in XRD and XPS, respectively, confirming the successful synthesis of Cu/MoS2. The prior band shift at the heterojunction causes efficient separation of photogenerated charge carriers and the shift of the position of Mo 3d to higher binding energies, which results in weaker intrinsic luminescence at 810 nm in the PL spectrum and smaller charge transfer resistance in the electrochemical impedance spectroscopy spectra, confirming the high PEC performance of the Cu/MoS2 composites. Meanwhile, the density functional theory calculations reveal that the energy of the d orbital of Mo in MoS2 decreases, which is helpful to accept electrons in Cu 3d. The Mo d track-occupancy introduced through the strong interplay between the most desirable combination of MoS2 and Cu will be accountable for such record-high performance. Therefore, this study makes a strong case for fine-tuning the electronic structures of PEC anode materials.