Photoinduced ferroelectric phase transition triggering photocatalytic water splitting

Utilizing two-dimensional (2D) ferroelectric semiconductors for photocatalytic water splitting (PWS) to produce clean hydrogen fuel shows promise but faces performance regulation challenges. This study employs real-time time-dependent density functional theory (rt-TDDFT) and first-principle calculations to propose a “one stone, two birds” strategy: light induces ferroelectric phase transitions and triggers PWS on monolayer Hf₂Ge₂S₆. Electronically, monolayer Hf₂Ge₂S₆ exhibits excellent stability, mechanical properties, an appropriate band gap, optimal band edge positions, and broad light absorption. Its ferroelectric (FE) phase promotes oxygen evolution reaction(OER), while the paraelectric (PE) phase enhances hydrogen evolution reaction(HER). Specifically, applying 10% compressive strain effectively suppresses OER on the FE phase, while a mere 2% tensile strain can induce complete spontaneity in HER on the PE phase. Finally, rt-TDDFT simulation results demonstrate that laser pulses can drive effective ion displacements of Ge atoms in monolayer Hf₂Ge₂S₆ and thereby generate the transition from FE to PE, which is attributed to the maintenance of charge distribution asymmetry through internal atomic electron transfers. More importantly, this recyclable ferroelectric photocatalyst, activated by light and electric fields, effectively prevents performance drawbacks from pure electric fields, demonstrating that a photoelectric alternating field can regulate PWS performance. These findings demonstrate that a photoelectric alternating field is an effective strategy to regulate photocatalytic performance for PWS.