A strategy to synergistically increase the number of active edge sites and the conductivity of MoS₂ nanosheets for hydrogen evolution

Abstract

Nanostructured MoS2 is very promising as an electrocatalyst for hydrogen evolution due to a greater number of active edge sites. However, a very large resistance between basal planes decreases the overall efficiency of hydrogen evolution, and greatly limits its application in industry. Herein we develop a facile strategy to synergistically increase the number of active edge sites and the conductivity of MoS2. MoS2 nanosheet arrays can be grown vertically on a carbon fiber cloth (CFC) substrates by a facile strategy. On the one hand, ammonium fluoride in the reaction system could effectively etch the inert basal plane of the MoS2 nanosheets, leading to the formation of pits in the inert basal plane of the MoS2 nanosheets. Thereby the number of active edge sites is significantly increased. On the other hand, the vertical growth of MoS2 nanosheet arrays on CFCs can significantly decrease the resistance of MoS2-based electrocatalysts. As a result, the MoS2-based electrocatalysts exhibit excellent catalytic activity for hydrogen evolution reactions, with a small Tafel slope and a large cathodic current density. Moreover, the CFC can be repeatedly utilized as a template to grow ultrathin MoS2 nanosheet arrays for HERs. The excellent activity and recyclable utilization, as well as mass production, indicate that the composite has promising applications in industry.

Hierarchical MoS2–rGO nanosheets with high MoS2 loading with enhanced electro-catalytic performance

“…As can be seen in Figure 6a, the onset potential for HER over the MoS 2 -rGO is -0.125 V, much positive than that of the MoS 2 (-0.2 V). Such a value of the MoS 2 -rGO is also more positive than the previously reported MoS 2 nanosheets with more complex nanostructures, [7][8] indicating the excellent HER activity of the sample. At a HER current density of 10 mA cm -2 which is regarded as the benchmark of application for practical electrochemical, [34][35][36] photo-catalytic and photo-elecrocatalytic cells, the overpotential of the MoS 2 -rGO is as low as 232 mV, adequate for practical applications.…”

“…And the exposed abundant edge of two-dimensional nanosheets enhances the reaction kinetics since it is well documented that the edge sites are more effective to HER and ORR than that of planar sites. [8,37] Furthermore, the rGO substrate with relatively good electrical conductivity and flexible nature provides a good buffering matrix to even better accommodate the microstructure change upon reactions. At the same time, the hierarchical micro/nano structure of the hybrid provides a reaction platform with enhanced reaction kinetics due to the nanostructured subunits and structural robustness of the panoramic micro-sized structure.…”

“…Besides tailoring microstructure of MoS 2 , [7][8] construction of hybrid structure between MoS 2 and conductive carbonaceous materials is considered as an effective strategy for improving the conductivity and stability of the MoS 2 -based electrode materials. [9][10][11][12][13][14][15][16][17][18][19][20][21] In general, carbonaceous materials in nanocomposite electrode materials are anticipated to serve dual functions as conducting agents to promote the electron transport in the poorly conductive MoS 2 , and probably more importantly as structure directing agents to enhance the stability of high-surface-energy MoS 2 (e.g.…”

Structural Engineering of Electrocatalysts for the Hydrogen Evolution Reaction: Order or Disorder?

“…These catalysts benefit from the high density of active edge sites of the porous structure as well as the fast electron transportation guaranteed by the conductive graphene support 38. Similarly, Yu and co‐workers prepared a composite catalyst based on etched MoS 2 nanosheet arrays that are vertically grown on carbon fiber cloth 39. The etching process can introduce active edge sites for HER, and the vertically aligned MoS 2 nanosheets on conductive carbon fibers can realize fast electron transportation during catalysis, finally enhancing the HER performance synergistically.…”

CoP Embedded in Hierarchical N‐Doped Carbon Nanotube Frameworks as Efficient Catalysts for the Hydrogen Evolution Reaction

“…Therefore developing highly active alternative nonprecious electrocatalyst is essential to satisfy the hydrogen generation industry. Consequently, enormous efforts have been devoted for the development of nanostructured non‐precious electrocatalysts with various compositions, such as transition metal chalcogenide, carbide, nitride, phosphide and boride …”