Ag 2 S nanoparticle-decorated MoS 2 for enhanced electrocatalytic and photoelectrocatalytic activity in water splitting.

In this article, a novel Ag ₂ S nanoparticle-decorated MoS ₂ composite (A@M) was synthesized through a facile in situ growth of the monoclinic crystallographic Ag ₂ S on MoS ₂ nanosheets. The A@M composite was used as a catalyst in water splitting which exhibits higher electrocatalytic and photoelectrocatalytic activity than the respective pure MoS ₂ and Ag ₂ S counterparts. Experimental results indicate that the as-prepared A@M composite with an optimal Ag ₂ S/MoS ₂ molar ratio of 16.30% (16%A@M) shows the best catalytic performance with low overpotentials (110 mV for V _oc , 190 mV for onset overpotential, 208 mV for the current density of 20 mA cm ^-2 ), a small Tafel slope (42 mV dec ^-1 ), and a high photocurrent (82 μA cm ^-2 under an applied potential of 0.4 V). The enhanced electrocatalytic activity is associated with the improved electrical conductivity resulting from the stretched MoS ₂ nanosheets and the enriched active sites due to the decorated Ag ₂ S particles. The formation of a type II heterojunction structure at the interface between Ag ₂ S and MoS ₂ facilitates the separation of photogenerated charge carriers, and thus is responsible for the enhanced photoelectrocatalytic activity and photocatalytic H ₂ production rate (628 μmol h ^-1 g ^-1 ). This work suggests a promising choice to overcome the intrinsic drawbacks of MoS ₂ nanostructures for the application in hydrogen evolution.