Mo thio and oxo-thio molecular complexes film as self-healing catalyst for photocatalytic hydrogen evolution on 2D materials

2D semiconducting nanosheets of Transition Metal Dichalcogenides are attractive materials for solar energy conversion because of their unique absorption properties. Here, we show that Mo thio- and oxo-thio-complexes anchored on 2D p-WSe2 nanosheets considerably boost water splitting under visible light irradiation with photocurrent density up to 2.0 mA cm−2 at -0.2 V/NHE. Besides developing high electro-catalytic activity, the Mo-complexes film is also shown to be capable of healing 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 supported by DFT calculations. In addition, the thio-, oxo-thio Mo complexes films are shown to enhance charge carrier separation and migration favouring the hydrogen evolution reaction, putting forward the use of thio-, oxo-thio-Mo complexes as a multicomponent passivation layer exhibiting multiple properties

Controlling 2D/2D Contacts in 2D TMDC Nanostructured Films for Solar-to-Hydrogen Conversion

With the objective to achieve high-performance photoactive 2D films, a variety of large-surface-area, nanostructured films composed of 2D transition metal dichalcogenides (TMDCs) building blocks was successfully self-assembled using a customized, surface-functionalized, metallic sulfide template. Since 2D/2D contacts in these nanostructured films were anticipated to play a crucial role in charge carrier transport properties, control of 2D/2D contact properties was explored by varying 2D building block sizes and film-forming processes. High-resolution transmission electron microscopy (HRTEM) deep characterization of morphological properties of 2D/2D contacts using focused ion beam (FIB) cross-sections reveals a variety of contact configurations mainly depending on the 2D building block thickness. Particularly, the effects of nanostructuration on 2D/2D contact characteristics such as the contact density, plane/plane vs edge/plane contact ratio, and contact boundary angles are clearly demonstrated on a large range of MoS2, WS2 and WSe2 building blocks varying from monolayers to nanoflakes, displaying various thicknesses. Correlations with electrical and photoelectrochemical properties demonstrate that the 2D/2D contact surface area, 2D/2D contact density, and contact boundary angles are key parameters controlling the recombination of photogenerated carriers. These findings are validated both on p-WSe2 and p-WS2 nanostructured films with photocurrents up to 4.5 mA cm–2 for the photoelectrochemical decomposition of H2O