Mo Thio and Oxo-Thio Molecular Complexes As Water-Soluble Self-Healing Catalysts for Photocatalytic Hydrogen Evolution on 2D Materials

Abstract

2D semiconducting nanosheets of Transition Metal Dichalcogenides are attractive materials for solar energy conversion because of their unique absorption properties. Recently, Hydrogen evolution reaction (HER) was achieved with thin 2D WSe2 nanosheets activated by well-known precious metal catalysts. Here, we propose noble-metal-free, Mo thio- and oxo-thio-complexes anchored on 2D p-WSe2 nanosheets for efficient water splitting under visible light irradiation with photocurrent density up to 2.0 mA cm-2 at -0.2 V/NHE. These Mo thio and oxo-thio- molecular complexes films represent an ideal class of catalysts, well-suited to functionalize 2D materials since they are stable in aqueous environments, cheap, environmentally benign to synthesize and process. Besides developing high electro-catalytic activity, the Mo complexe films were shown to display ability to heal surface defects. We propose that the observed healing of surface defects arises from the strong adsorption on point defects of the 2D WSe2 substrate of Mo-complexes such as (MoS4)2-, (MoOS3)2-, (Mo2S6O2)2- as shown from DFT calculations. In addition to display catalytic and healing effects, the thio-, oxo-thio Mo complexes films which spontaneously formed at well-defined pH were shown to enhance charge carrier separation and migration for the Hydrogen Evolution Reaction, thus representing an example of multicomponent passivation layer exhibiting multiple properties.