g-C3N4 integrated with MoS2/BiVO4 as a 2D/2D/1D heterojunction for enhanced photocatalytic activity under sunlight and DSSC performances

Abstract

In this work, MoS₂/BiVO₄/g-C₃N₄ as a 2D/2D/1D ternary heterojunction was synthesized by a sonication assisted hydrothermal method for photodegradation of organic dye pollutants under direct sunlight and serves as counter electrodes for dye-sensitized solar cells (DSSC). The MoS₂/BiVO₄/g-C₃N₄ nanohybrid was confirmed to have a crystal structure using X-ray diffraction angles presented at 14.45°, 26.83° and 28.44°, its functional groups were shown by FT-IR spectroscopy at 598, 474 and 804 cm⁻¹ , its chemical composition was shown by XPS spectroscopy, including Mo 3d, S 2p, O 1 s, C 1 s, Bi 4 f, V 2p and N 1 s, optical studies were observed by UV-DRS spectroscopy at 652, 579 and 460 nm, and it had a narrowing band gap at 1.83 eV, respectively. Further SEM and HR-TEM studies display that self-assembled g-C₃N₄ nanorods and BiVO₄ nanoflakes were decorated on the MoS₂ nanosheet surface, formed as 2D/2D/1D nanostructures. In photocatalytic activity of crystal violet (CV) and rhodamine B (RhB) dyes for all samples, the MoS₂/BiVO₄/g-C₃N₄ hybrid exhibited the highest degradation efficiencies of 98 % and 96 %, respectively. The investigations of ESR, radical trapping, Mott-Schottky test and photoluminescence (PL) spectra strongly provide evidence for the Z-scheme catalytic mechanism of the MoS₂/BiVO₄/g-C₃N₄ hybrid. The MoS₂/BiVO₄/g-C₃N₄ counter electrode based fabricated DSSC exhibits J_sc, V_oc, FF % and power conversion efficiency (PCE %) of 5.54 mA cm⁻², 0.713 V, 0.63 % and 2.48 %, respectively, which is 2.6 times higher than the as-prepared DSSC from pristine MoS₂. The enhanced photocatalytic and photovoltaic activities were attributed to improved charge separation, shorter charge transfer distance, and stronger interfacial interaction by forming a Z-scheme (N-P-N) heterojunction between MoS₂, BiVO₄, and g-C₃N₄. This research is expected to provide new insights into the rational design and fabrication of highly effective Z-scheme MoS₂/BiVO₄/g-C₃N₄ as 2D/2D/1D nanohybrid for photocatalytic processes for wastewater treatment and DSSC energy conversion harvesting.