Highly Efficient Electrocatalytic Hydrogen Production by MoS_x Grown on Graphene‐Protected 3D Ni Foams

Abstract

A three-dimensional Ni foam deposited with graphene layers on surfaces is used as a conducting solid support to load MoS(x) catalysts for electrocatalytic hydrogen evolution. The graphene sheets grown on Ni foams provide robust protection and efficiently increase the stability in acid. The superior performance of hydrogen evolution is attributed to the relatively high catalyst loading weight as well as its relatively low resistance.

A Flexible Platform Containing Graphene Mesoporous Structure and Carbon Nanotube for Hydrogen Evolution

“…The S2p spectrum is fitted by three doublets, including elemental S 0 at 163.9 eV, bridging S 2 2− at 163.2 eV, and terminal S 2− located at 162.1 eV (Figure 3d). The atomic ratio of S to Mo is 3.4, corresponding to MoS 3 plus elemental sulfur, in good accordance with Equation (1) and previous reports 24, 29…”

“…(2) The platform has good electrical conductivity and maintains intimate contact with MoS x , which ensures the effective transport of electrons during the electrochemical process. (3) Plenty of uncoordinated sulfur atoms exist over the entire surface of amorphous MoS x to serve as the active sites for the HER 24, 29. For example, XPS characterization has confirmed the existence of bridging S 2 2− and apical S 2− on the surface of the amorphous catalyst.…”

“…The electrochemical performance of MoS x catalysts can be improved not only by increasing active sites but also by employing suitable conductive substrates26 such as Au,6 carbon nanotubes (CNTs),27 carbon cloth,13, 14 ordered mesoporous carbon,28 and graphene 8, 29. Porous substrates have large surface area, which facilitates the nucleation of MoS x to give abundant active sites and contributes to their facile contact with the electrolyte.…”

“…Porous substrates have large surface area, which facilitates the nucleation of MoS x to give abundant active sites and contributes to their facile contact with the electrolyte. Highly conductive carbonaceous materials can also notably expedite electron transfer 29. Moreover, their stable chemical property in acid solution ensures stable catalysis.…”

Solvent-Assisted Oxygen Incorporation of Vertically Aligned MoS2 Ultrathin Nanosheets Decorated on Reduced Graphene Oxide for Improved Electrocatalytic Hydrogen Evolution

“…Tafel slope of the O-MoS 2 /rGO is shown in Figure 6b, suggesting a highly efficient catalytic performance with a small slope around 40 mV/decade (lower than many reported MoS 2 -based catalysts in Figure S7), 1,4−6,21,38,51−57 and the Volmer-Heyovsky mechanism associated with electrochemical desorption step as the rate-limiting step. 1,5,51 The durability test for O-MoS 2 /rGO catalyst indicates that only 1.3% loss in the current density even after continuous 2000 cycles (Figure 6a), without any clear morphology and element constituent changes ( Figure S8). Such excellent HER performance of O-MoS 2 /rGO catalysts could be rationalized as follows: (i) the incorporated oxygen from DMF solvent improves the intrinsic conductivity (the resistivities of O-MoS 2 /rGO, pristine MoS 2 /rGO, and annealed O-MoS 2 /rGO catalyst films spin-coated on SiO 2 /Si substrates obtained by four-point-probe system are 3.3 × 10 −2 Ω·cm, 0.25 Ω·cm, and 0.12 Ω·cm, respectively), promoting fast mobility of the electron along the MoS 2 nanosheets; 7,40 (ii) oxygen incorporation increases the defect and vertical edge ratio, giving more exposed Mo and S edges to participate catalytic process; 58 (iii) in situ synthesis of O-MoS 2 /rGO through hydrothermal method results in the pronounced synergetic effect between MoS 2 nanosheets and rGO with better mechanical adhesion and stability (see Supporting Information on the electrochemical behavior of mechanical mixture of OMoS 2 and rGO in Figure S9).…”