Two-dimensional C20-based monolayers and heterostructures for photocatalytic overall water splitting

Abstract C 20 , as the smallest carbon cage, possesses unique properties but has not been extensively explored for photocatalytic overall water splitting. This study proposes three two-dimensional (2D) C 20 -based monolayers ( α -C 20 , β -C 20 , and γ -C 20 ) as potential photocatalysts for efficient water splitting with direct Z-scheme. α -C 20 monolayer has ideal band edges for hydrogen evolution reaction (HER) with a Gibbs free energy of 0.0147 eV. GeS 2 / α -C 20 , MoS 2 / β -C 20 , SnS 2 / β -C 20 , and SnSSe/ β -C 20 heterostructures are developed. However, γ -C 20 -based heterostructures did not meet the Z-scheme requirements. Notably, the solar-to-hydrogen (STH) efficiency for the SnSSe/ β -C 20 heterostructure can reach 27.54%. The favorable Gibbs free energies indicate that both HER and oxygen evolution reaction (OER) can occur spontaneously within suitable pH ranges. Nonadiabatic molecular dynamics simulations show that the lifetimes of photoexcited carriers in the GeS 2 / α -C 20 heterostructure are in the nanosecond range, suggesting robust photocatalytic activity. These results offer valuable insights into the potential of C 20 -based photocatalysts for water-splitting applications.