Direct Z-scheme SnC/InP heterostructure photocatalyst for overall water-splitting with broad optical absorption and strong catalytic activity

Abstract

We investigate a SnC/InP heterostructure using first-principles calculation. The most stabilized C3 configuration belongs to a type-II band alignment with a smaller bandgap of 1.06 eV than those of 1.79 eV and 1.75 eV for InP and SnC monolayers respectively. The electrons migrate from SnC side to InP side, generating a built-in electric field from SnC to InP and band edge bending at the interface. Combining this small bandgap and the band edge offset demonstrates that the photogenerated carriers are transported along a direct Z-scheme pathway. Furthermore, the free energy of the hydrogen evolution reaction exhibits a negative value, implying that hydrogen can be spontaneously reduced. At the same time, the oxygen evolution reaction also becomes thermodynamically spontaneous upon applying an external potential 3.08 V. The SnC/InP heterostructure exhibits broad light absorption with peak value up to 3.86 × 10⁵ cm⁻¹ at 2.9 eV in the visible light region. In addition, the higher solar-to‑hydrogen efficiency 15.35 %, strong catalytic activity under acidic, neutral and alkaline environments as well as large strain range from −4 % to 4 % confirm the tremendous potential of the SnC/InP heterostructure in photocatalytic overall water-splitting.