To achieve photoelectrochemical (PEC) activity of MoS₂ for hydrogen production through water splitting, the band edges of MoS₂ should match with the hydrogen and oxygen production levels. Our first-principles calculations show that the band edges of monolayer MoS₂ can be effectively tuned by surface ligand functionalization, resulting from the intrinsic dipole of the ligand itself and the induced dipole at the ligand/MoS₂ interface. We further explore the influence of ligand coverage, ligand functionalization and the substrate on the band structure of MoS₂. The hybrid C₆H₅CH₂NH₂/MoS₂/graphene structures may be compelling candidates as they satisfy the stringent requirements of PEC water splitting.