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Graphene/Group 5 Transition Metal Dichalcogenide Composites for Electrochemical Applications.

In comparison to the extensive research and great success attained by Group 6 transition metal dichalcogenides (TMDs) as hydrogen evolution reaction (HER) electrocatalysts, there is limited research focused on metallic Group 5 TMDs for use as electrocatalysts for hydrogen evolution. Density functional theory calculations have pointed out that Group 5 TMDs are highly favorable for HER, especially vanadium disulfide. In this work, nanocomposites of graphene and Group 5 TMDs were synthesized by thermal exfoliation of graphene oxide/TMD precursors in an H2 S atmosphere or in a H2 atmosphere as a control. Graphene oxide was prepared by the Hummers method while vanadium tetrachloride, niobium pentachloride, and tantalum pentachloride were utilized as TMD precursors. Then the potential of these nanocomposites as electrocatalysts towards HER was explored. Although these nanocomposites do not have comparable HER performance to Group 6 TMDs, they exhibit higher electrocatalytic activity in comparison with thermally reduced graphene oxide (TRGO) in the absence of TMD modification. In addition, the capacitive performance of these materials was also investigated in consideration of the high capacitance of graphene. It was indicated that the presence of TMDs on graphene actually suppress the capacitance performance of graphene itself.