Visible Light-Driven Photoelectrocatalytic Water Splitting Using Z-Scheme Ag-Decorated MoS₂/RGO/NiWO₄ Heterostructure

Herein, we have successfully constructed a solid-state Z-scheme photosystem with enhanced light absorption capacity by combining the optoelectrical properties of AgNPs with those of the MoS₂/RGO/NiWO₄ (Ag-MRGON) heterostructure. The Ag-MRGON Z-scheme system demonstrates improved photo-electrochemical (PEC) water-splitting performance in terms of applied bias photon-to-current conversion efficiency (ABPE), which is 0.52%, and 17.3- and 4.3-times better than those of pristine MoS₂ and MoS₂/NiWO₄ photoanodes, respectively. The application of AgNPs as an optical property enhancer and RGO as an electron mediator improved the photocurrent density of Ag-MRGON to 3.5 mA/cm² and suppressed the charge recombination to attain the photostability of ∼2 h. Moreover, the photocurrent onset potential of the Ag-MRGON heterojunction (i.e., 0.61 V_RHE) is cathodically shifted compared to those of NiWO₄ (0.83 V_RHE), MoS₂ (0.80 V_RHE), and MoS₂/NiWO₄ heterojunction (0.73 V_RHE). The improved PEC water-splitting performance in terms of ABPE, photocurrent density, and onset potential is attributed to the facilitated charge transfer through the RGO mediator, the plasmonic effect of AgNPs, and the proper energy band alignments with the thermodynamic potentials of hydrogen and oxygen evolution.