Formation of P-N Heterojunctions by Incorporation of Mn2+ into the CdS Lattice Toward Highly Efficient Photocatalytic H2 Evolution

The synthesis of Cd1-xMnxS solid solutions (x = 0.0, 0.25, 0.5, 0.75, and 1.0) has been achieved through a facile hydrothermal route. Because of the limited mutual solubility between CdS and gamma-MnS, the incorporation of Mn2+ into CdS lattice simultaneously produced CdS-hosted Cd1-xMnxS and gamma- MnS-hosted Cd1-xMnxS phases during the hydrothermal synthesis of Cd1-xMnxS solid solutions, especially at x = 0.5. The Cd1-xMnxS solid solutions with the coexisting dual phases exhibit remarkably higher photocatalytic H2 evolution from water splitting than pristine CdS. The influences of the incorporation of Mn2+ into the CdS lattice on the phase structure and compositions, morphologies, BET surface area, band structures, semiconductor characteristics, photoinduced charge separation, and resulting H2 evolution were investigated in detail. It was well revealed that the coexistence of CdS-hosted Cd1-xMnxS and gamma-MnS-hosted Cd1-xMnxS phases in the solid solutions constructs the p-n heterojunctions with an appropriate band alignment, which effectively facilitates the transfer and separation of the photogenerated charges for the highly efficient H2 evolution. Moreover, the charge separation and photocatalytic H2 evolution over the Cd1-xMnxS solid solutions can be further improved by the deposition of Ni(OH)2 as a cocatalyst.