Co3O4 modified Mn0.2Cd0.8S with different shells forms p-n heterojunction to optimize energy/mass transfer for efficient photocatalytic hydrogen evolution

The construction of an unique structure to optimize the energy/mass transfer for photocatalysts is an effective way to improve their solar-chemical energy conversion efficiency. Here, p-type Co3O4 polyhedrons and n-type Mn0.2Cd0.8S microrods were successfully coupled to construct Mn0.2Cd0.8S/Co3O4 p-n heterojunction. In order to optimize the energy/mass transfer in the Mn0.2Cd0.8S/Co3O4 p-n heterojunction photocatalyst, ZIF-67 was used as precursor to create hollow Co3O4 derivatives [Co3O4 porous polyhedrons (PPs), Co3O4 hollow double-shell polyhedrons (HDSPs), and Co3O4 hollow single-shell polyhedrons (HSSPs)]. And Co3O4 hollow single-shell polyhedrons (HSSPs) possesses these prominent advantages that strong light trapping ability, short carrier transport distance, and larger catalyst/solvent contact area in comparison with other two derivatives. More importantly, the band structures of the differently structural Co3O4 are distributed stepwise. The valence band potential of Co3O4 HSSPs is more positive meaning stronger oxidation ability, which effectively improves the separation efficiency of electron-hole pairs in Mn0.2Cd0.8S/Co3O4 p-n heterojunction system. Therefore, Mn0.2Cd0.8S/Co3O4 HSSPs showed more excellent hydrogen evolution activity (11222 μmol g−1 h−1) which was about 26 times and 2.34 times that of Mn0.2Cd0.8S and Mn0.2Cd0.8S/Co3O4 PPs, respectively. This work will provide broad prospects for the rational design of efficient photocatalysts.