Overall Water Splitting of the Direct Z-Scheme vdW Heterojunction GeC/ZrS2

Abstract

Direct Z-scheme heterojunctions can realize the effective space separation of electrons and holes under light radiation. Therefore, it has an obvious advantage for water splitting. In this work, we have designed and studied a new heterojunction, GeC/ZrS₂, with a direct Z-scheme band arrangement. Both monolayer GeC and monolayer ZrS₂ in the present GeC/ZrS₂ heterojunction are easily prepared. We also systematically investigated the electronic and optical properties of the GeC/ZrS₂ heterojunction. The calculated binding energy and phonon spectra show that the GeC/ZrS₂ heterojunction has good stability. The electronic structure and band arrangement show that GeC/ZrS₂ is a direct Z-scheme energy band arrangement with a suitable band gap (1.19 eV) for photocatalytic water decomposition. The GeC/ZrS₂ heterojunction shows good absorption coefficients (reaching 10⁵ cm^–1) in the visible and ultraviolet ranges. The GeC/ZrS₂ heterojunction has excellent carrier mobilities in both the armchair and zigzag directions, and the electron mobility can reach 1502.78 cm² V^–1 s^–1 in the zigzag direction, which is good for the space separation of electrons and holes under light radiation. The Gibbs free energy shows that the GeC/ZrS₂ heterojunction can achieve overall water splitting at pH = 14 and an external voltage of 3.3 eV. The solar to hydrogen (STH) production efficiency is 28.7%. Moreover, the GeC/ZrS₂ heterojunction can achieve a direct Z-scheme band arrangement, and the biaxial strain can further increase the band gap and improve the photocatalytic performance. Our results show that the heterojunction GeC/ZrS₂ has excellent potential for overall photocatalytic water splitting.