One-Pot Rapid Synthesis of Mo(S,Se)₂ Nanosheets on Graphene for Highly Efficient Hydrogen Evolution

Abstract

The electrocatalytic hydrogen evolution reaction (HER) is known to be an important technique for efficient hydrogen production, and the development of a highly active electrocatalyst with lower overpotential is a key issue. In this study, we demonstrated the rapid, one-pot synthesis of highly active molybdenum dichalcogenide/ reduced graphene oxide (Mo(S,Se)/rGO) electrocatalysts from cost-effective and environmentally friendly substances using reductive supercritical conditions. We found that edgerich MoS 2 is synthesized under a high-density ethanol condition and successfully controlled the composition of molybdenum dichalcogenide (MoS 2−x Se x ) nanoflowers at the atomic level by varying the ratio of chalcogen sources. The electrocatalytic HER activity increased with the formation of an edges-rich structure and a solid solution of MoS 2 and MoSe 2 , and by complexing with graphene. The synthesized MoS 0.9 Se 1.1 /graphene showed excellent HER properties that can be categorized into the highest-activity group of the previously reported molybdenum dichalcogenide and its composite. Such high electrocatalytic HER performance should be the result of optimizing the hydrogen adsorption free energy of MoS 2−x Se x and effectively forming conductive paths between MoS 0.9 Se 1.1 and graphene. This rapid one-pot process using supercritical ethanol will be suitable for the mass production of highly active molybdenum dichalcogenide electrocatalysts.

Earth‐Abundant Transition‐Metal‐Based Electrocatalysts for Water Electrolysis to Produce Renewable Hydrogen

“…An extremelyl ow Tafel slope of 30 mV dec À1 can be expected for MoS 2 nanowires grown on Au (755) surfaces according to ac alculated kinetic barriero f0 .49 eV on the Mo edges, suggesting the Volmer-Ta fel mechanism.N i(755) and Cu (755) were predictedt oa ct as the alternative substrates of Au (755) to support MoS 2 and maintain the same activity. [28] Chemical exfoliation can also be used to prepare monolayered WS 2 nanosheets, which exhibited considerable activity for hydrogen evolution reactione ven under very low overpotentials (80-100 mV) with aT afel slope of 55 mV dec À1 .Ahigh concentration of strains, caused by zigzag-like local lattice distortions in metallic 1T-WS 2 nanosheets, was assumedi mportant for facilitatingh ydrogen evolution reaction( Figure 5). Chhowalla and co-workersn oticed that electrochemical oxidation of the edge sites played less impact on catalytic activity of 1T-MoS 2 than 2H-MoS 2 ,suggesting the catalytical activity of basal plane.M eanwhile, they emphasized the critical role of charge-transfer kinetics in promoting the hydrogen evolution activity of MoS 2 .…”

“…The Tafel slopes varied from 82 mV dec À1 (MoS 2 )t o4 8mVdec À1 (MoS 0.8 Se 1.2 ). [28] Chemical exfoliation can also be used to prepare monolayered WS 2 nanosheets, which exhibited considerable activity for hydrogen evolution reactione ven under very low overpotentials (80-100 mV) with aT afel slope of 55 mV dec À1 .Ahigh concentration of strains, caused by zigzag-like local lattice distortions in metallic 1T-WS 2 nanosheets, was assumedi mportant for facilitatingh ydrogen evolution reaction( Figure 5). [29] The WS 2 /WS 3 material was synthesized through an electrochemical method.T he obtained product possessed ac ompositiono f WS 2.64 and ac hain-likes tructure consisting of S 2À and S 2 2À li- gands,l eading to different metal-chalcogen binding strengths in the WS 2.64 electrocatalyst.…”

Earth-Abundant Electrocatalysts in Proton Exchange Membrane Electrolyzers

“…Another approach that has produced promising results is to deposit molybdenum sulfide onto something highly conducting and/or with high surface area, like nanotubes, nanowires, reduced graphene oxide etc. [93][94][95][96]. Depending on the methods used, one often ends up with amorphous MoS x .…”

Earth-Abundant Electrocatalysts in Proton Exchange Membrane Electrolyzers

“…Another approach that has produced promising results is to deposit molybdenum sulfide onto something highly conducting and/or with high surface area, like nanotubes, nanowires, reduced graphene oxide etc. [93][94][95][96]. Depending on the methods used, one often ends up with amorphous MoSx.…”