Amorphous molybdenum sulfide/polymeric carbon nitride composite with multiple interfaces for boosting photoelectrochemical water splitting performance

Abstract

Rational interface design is an important way to improve the photoelectrochemical activity of catalysts in the sustainable energy and the environment. Herein, we simultaneously realize the construction of polymeric carbon nitride (PCN)-based homojunction (HPCN) and amorphous molybdenum sulfide (a-MoSx) /PCN heterojunction (a-MoSx/HPCN) in the composite catalyst system by one-pot calcination. The presence of a-MoSx was confirmed by X-ray photoelectron spectroscopy (XPS) and element mapping. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed the amorphous characteristics of molybdenum sulfide. The photoluminescence (PL) spectroscopy indicated that the photo-generated carrier recombination of composite is effectively inhibited after constructing the homojunction and loading molybdenum sulfide. The confined effect of the PCN matrix induced the formation of ultrafine size a-MoSx, and its co-catalyst function is prominent. The optimized composite catalyst showed obvious boosting activity in photoelectrochemical water slitting. Photocathode current of −161 μA cm−2 (0 V vs. RHE) and photoanode current of 10 μA cm−2 (1.23 V vs. RHE) are almost 12 and 5 times than single PCN homojunction under the irradiation of 25 W light-emitting diode light source. This boosted activity can be attributed to the multiple interface effect of the n-n junction of PCN/PCN and the p-n junction of a-MoSx/PCN as well as the co-catalysis of amorphous molybdenum sulfide. The synergies between various merits effectively improved the absorption of visible light, the separation of photogenerated electrons and holes, and the addition of more reactive sites. This paper provides a new idea for interface engineering of PCN-based composite photoelectrode.