Two-dimensional type-II MSi2N4/InS (M = Mo, W) heterostructures for photocatalysis

Recently, two-dimensional (2D) ternary monolayer MSi2N4 (M = Mo, W) was synthesized by chemical vapor deposition. However, monolayer MSi2N4 (M = Mo, W) has an indirect bandgap, which seriously hinders its application in optoelectronic devices. Herein, we propose two MSi2N4/InS (M = Mo, W) van der Waals heterojunctions (vdWHs) possessing type-II band alignments by first-principles. Our results indicate that these vdWHs achieve an indirect-to-direct bandgap transition and exhibit fascinating optical absorption spectra in the range of visible light. Moreover, the light absorption efficiencies of both vdWHs are significantly strengthened, and the intrinsic electric field of vdWHs can effectively promote the separation of photogenerated electron–hole pairs. In particular, the most significant electron mobility of MSi2N4/InS (M = Mo, W) vdWHs is up to 6.6 × 103 cm2 V−1 s−1, demonstrating their considerable potential for optoelectronic device applications. Notably, MSi2N4/InS (M = Mo, W) vdWHs can facilitate water splitting due to their suitable band edges. Therefore, our findings demonstrate two 2D MSi2N4/InS (M = Mo, W) type-II vdWHs with fascinating potentials for photocatalysis.