Direct Z-scheme GaSe/ZrS2 heterojunction for overall water splitting

In this paper, a novel GaSe/ZrS2 heterojunction is designed and systematically studied. The monolayers in this heterojunction can be easily fabricated and the heterojunction has good stability. More importantly, electronic structures, band alignment, differential charge density and the built-in electric field show that it is a direct Z-scheme photocatalyst that can not only effectively separate photogenerated carriers but also improve the redox ability of carriers. The mobility of the electrons in this heterostructure is as large as 1450.38 cm2V−1s−1 (same magnitude order of black phosphorene) along the zigzag direction, which is beneficial to photocatalytic performance. The band alignment shows that GaSe/ZrS2 is suitable for overall water splitting and the splitting can happen spontaneously. Moreover, GaSe/ZrS2 heterojunction has excellent absorption coefficients (higher than 105cm−1) in both visible and ultraviolet ranges which is very beneficial to photocatalytic overall water splitting. The study of electric field and biaxial strain effects on GaSe/ZrS2 heterojunction show that the light absorption coefficients of GaSe/ZrS2 heterojunction can be obviously further improved by applying biaxial strain. Our work shows that GaSe/ZrS2 heterojunction is a promising photocatalysts for overall water splitting.