Improved Hydrogen Evolution Reaction Performance using MoS₂–WS₂ Heterostructures by Physicochemical Process

Abstract

This report describes the synthesis of a layered molybdenum disulfide (MoS2)–tungsten disulfide (WS2) heterostructure onto fluorine doped tin oxide covered glass substrates using a combination of chemical bath deposition and RF sputtering techniques. FESEM images revealed that the MoS2–WS2 heterostructure surface consisted of a cauliflower structured array of grains with spherical structures. The vertically aligned atomic layers were explored by transmission electron microscopy images for MoS2–WS2 heterostructure. Hydrogen evolution reaction (HER) kinetics show overpotentials of 151 and 175 mV @ 10 mA/cm2 with Tafel slope values of 90 and 117 mV/decade for pristine MoS2 and WS2 electrocatalysts, respectively. Improved electrocatalytic activity for HER was established with overpotential 129 mV @ 10 mA/cm2 and Tafel slope 72 mV/decade for the MoS2–WS2 heterostructure. The MoS2–WS2 heterostructure electrocatalyst showed robust continuous HER performance over 20 h in an acidic solution. This improved electrochemical performance emerges from the elevation of electron–hole separation at the layer interfaces and sharing of active edge sites through the interface. This study provides the basis to develop new applications for transition-metal dichalcogenides heterostructures in future energy conversion systems.

Engineered 2D Transition Metal Dichalcogenides—A Vision of Viable Hydrogen Evolution Reaction Catalysis

“…For example, Vikraman et al demonstrated the improved HER performance using MoS 2 –WS 2 heterostructures owing to the elevation of electron–hole separation at the layer interfaces and sharing of active edge sites through the interface. [ 157 ] Kwon et al have improved the HER catalytic performance of MoS 2 through the formation of n‐TMD/p‐TMD heterojunctions to use the high electric fields in the p–n junction. [ 158 ] Although the fabrication of these materials is not simple enough, the concept of the adhesion energy and charge injection can be well employed in building the hybrid structure that we have discussed above.…”

“…Another powerful aspect of TMD catalysis that can be used in complement to the techniques we have discussed is the fabrication of chemically functionalized TMDs, these functionalities can include noble metals as we have discussed above, and also the metal organic frameworks, layered perovskites, hybrid structures or organic group functionalization. [ 156–158,192–196 ] This is an emerging a powerful field as it opens a whole new set of possibilities to active the catalytically active sites of TMDs and add catalytic activity, via the functional moiety, to inactive sites on the pristine TMD for both acidic and alkaline HER. Since heterostructuring is hugely flexible owing to van der Waals stacking, unique electronic band structures (e.g., tune the Δ G H* and enable improved charge injection between interfaces) can be fabricated and tested in an extremely simple and controllable manner.…”

“…[ 127,128,133–136 ] Together with some doping strategies, it also supports the alkaline HER of TMDs based materials. [ 156–158 ] While heterostructuring will need to be supported by robust DFT calculations. [ 197 ] It unlocks a plethora of potential material combinations and a whole new field of potential HER catalysts.…”

Dependence of the Properties of 2D Nanocomposites Generated by Covalent Crosslinking of Nanosheets on the Interlayer Separation: A Combined Experimental and Theoretical Study

“…To enhance the HER activity of MoS 2 , theoretical and experimental studies have proposed anchoring of Co atoms and cobaloxime on the inert basal plane of MoS 2 , engineering in the defects sites and using metallic 1T‐MoS 2 . Remarkable advances in heterostructure designs such as MoS 2 /graphene superlattices, nanosized MoS 2 /graphene hybrids, nonmetal plasmonic MoS 2 /TiO 2 heterostructure and MoS 2 ‐WS 2 heterostructures by physiochemical process have led to enhanced HER activity . Some studies have also revealed enhanced HER activity by virtue of active sites –…”

“…[13] Remarkable advances in heterostructure designs such as MoS 2 /graphene superlattices, [14] nanosized MoS 2 /graphene hybrids, [15] nonmetal plasmonic MoS 2 /TiO 2 heterostructure [16] and MoS 2 -WS 2 heterostructures by physiochemical process have led to enhanced HER activity. [17] Some studies have also revealed enhanced HER activity by virtue of active sites. [18a-d] Covalently cross-linked graphene sheets have been investigated primarily for the surface area and gas adsorption properties.…”