Exploring the Ti2CO2–WSe2 Heterostructure as a Direct Z-Scheme Photocatalyst for Water Splitting: A Non-Adiabatic Study

One of the potential strategies to solve renewable energy shortage is to design low-cost efficient photocatalysts for water splitting to aid hydrogen and oxygen evolution reactions (HER and OER). Two-dimensional (2D) materials like MXenes and transition metal dichalcogenides (TMDs) have caught special attention owing to their unique optical, electrical, and mechanical properties, but come with issues like photocorrosion and poor charge separation. Bilayer vdW heterojunctions of suitable constitutive monolayers are coming up as a potential solution to these hazards, accredited to their tunable band gap and efficient charge separation. In this paper, we have investigated the possibility of Ti2CO2–WX2 (X = S, Se, Te) vdW heterostructures to perform as Z-scheme photocatalysts by employing first-principle density functional calculations, and thereby, the Ti2CO–WSe2 heterostructure has emerged as the most promising material for Z-scheme photocatalysis. Further, excited-state dynamics simulation reveals that the timescales of electron transfer and hole transfer are greater (1.13 and 1.22 ps, respectively) than the maximum time limit of the photogenerated electron–hole recombination (1.0 ps) owing to the weaker non-adiabatic coupling and electron–phonon coupling. This affirms the fact that photogenerated electrons and holes with greater redox ability are preserved to drive the photocatalytic pathway. In addition to that, the free energy calculations associated with the HER and OER processes entail that the processes occur spontaneously on the surface of the heterostructure without any co-catalyst. This establishes the Ti2CO–WSe2 heterostructure as a potential mediator-free direct Z-scheme photocatalyst for overall water splitting.