Design of a p-n heterojunction in 0D/3D MoS 2 /g-C 3 N 4 composite for boosting the efficient separation of photogenerated carriers with enhanced visible-light-driven H 2 evolution.

Constructing a 0D/3D p-n heterojunction is a feasible strategy for accelerating photo-induced charge separation and promoting photocatalytic H 2 production. In this study, a 0D/3D MoS 2 /g-C 3 N 4 (0D/3D-MCN) photocatalyst with a p-n heterojunction was prepared via a facile light-assisted deposition procedure, and the 3D spongy-like g-C 3 N 4 (3D-CN) was synthesized through simple thermolysis of NH 4 Cl and melamine mixture. For comparison, 2D-MoS 2 nanosheets were also embedded in 3D-CN by a solution impregnation method to synthesize a 2D/3D-MCN photocatalyst. As a result, the as-prepared 0D/3D-MCN-3.5% composite containing 3.5 wt% 0D-MoS 2 QDs exhibited the highest photocatalytic H 2 evolution rate of 817.1 μmol h -1 g -1 , which was 1.9 and 19.4 times higher than that of 2D/3D-MCN-5% (containing 5 wt% 2D-MoS 2 nanosheets) and 3D-CN, respectively. The results of XPS and electrochemical tests confirmed that a p-n heterojunction was formed in the 0D/3D-MCN-3.5% composite, which could accelerate the electron and hole movement in the opposite direction and retard their recombination; however, it was not found in 2D/3D-MCN-5%. This study revealed the relationship among the morphologies of MoS 2 using g-C 3 N 4 as a substrate, the formation of a p-n heterojunction, and the H 2 evolution activity; and provided further insights into fabricating a 3D g-C 3 N 4 -based photocatalyst with a p-n heterojunction for photocatalytic H 2 evolution.