A two-dimensional MoS2/WSe2 van der Waals heterostructure for enhanced photoelectric performance.

• The photoelectric performance of MoS2/WSe2 heterojunctions was studied in a PEC cell. • Heterojunctions were fabricated via liquid-phase exfoliation and vacuum filtration. • The band alignment of the heterojunctions was established with the support of XPS. • The mechanism of the photoelectrochemistry process was revealed. Fabricating a two-dimensional (2D) van der Waals heterostructure is an efficient strategy to improve the photoelectric performance of 2D materials, thus providing a new possibility for the photoanode material design in photoelectrochemistry (PEC) devices. Herein, transition metal dichalcogenide (TMD) MoS 2 /WSe 2 heterojunction photoelectrodes are prepared via liquid-phase exfoliation and vacuum filtration. Linear sweep voltammetry, transient photocurrent, and open circuit potential measurements show that the heterojunction photoelectrodes have enhanced photocurrent intensity and improved photoresponse activity. Moreover, Nyquist impedance plots, Bode phase plots, and Mott-Schottky measurements demonstrate that the heterojunction samples have higher charge transfer rate and longer charge lifetime than MoS 2 and WSe 2. To reveal the mechanisms, the band alignment of MoS 2 /WSe 2 heterojunction samples is established with the support of X-ray photoelectron spectroscopy and first-principles theory calculation. Accordingly, the improved PEC performance of the heterojunction photoanode is ascribed to the built-in electric field between MoS 2 and WSe 2 nanosheets, which promotes the photogenerated e-h pair separation and suppresses their recombination. This work verifies the PEC mechanism of MoS 2 /WSe 2 heterojunction photoelectrodes, which is significant for the design of PEC devices based on TMD heterostructures. [ABSTRACT FROM AUTHOR]