Unsaturated Sulfur Edge Engineering of Strongly Coupled MoS₂ Nanosheet–Carbon Macroporous Hybrid Catalyst for Enhanced Hydrogen Generation

Abstract

The low hydrogen adsorption free energy and strong acid/alkaline resistance of layered MoS2 render it an excellent pH‐universal electrocatalyst for hydrogen evolution reaction (HER). However, the catalytic activity is dominantly suppressed by its limited active‐edge‐site density. Herein, a new strategy is reported for making a class of strongly coupled MoS2 nanosheet–carbon macroporous hybrid catalysts with engineered unsaturated sulfur edges for boosting HER catalysis by controlling the precursor decomposition and subsequent sodiation/desodiation. Both surface chemical state analysis and first‐principles calculations verify that the resultant catalysts exhibit a desirable valence‐electron state with high exposure of unsaturated sulfur edges and an optimized hydrogen adsorption free energy, significantly improving the intrinsic HER catalytic activity. Such an electrocatalyst exhibits superior and stable catalytic activity toward HER with small overpotentials of 136 mV in 0.5 m H2SO4 and 155 mV in 1 m KOH at 10 mA cm−2, which is the best report for MoS2–C hybrid electrocatalysts to date. This work paves a new avenue to improve the intrinsic catalytic activity of 2D materials for hydrogen generation.

Experimental and Theoretical Insights of MoS2/Mo3N2 Nanoribbon‐Electrocatalysts for Efficient Hydrogen Evolution Reaction

“…The binding energy pairs centered at ∼162.41 and ∼163.63 eV are attributable to S 2p 3/2 and S 2p 1/2 of divalent sulfide ions (S 2− ), respectively. These are in well agreement with the reported values for MoS 2 crystals . Compared with the MoS 2 /Mo 3 N 2 hybrid sample, the peaks assigned to S 2p 3/2 and S 2p 1/2 for the MoS 2 sample shift towards lower binding energies (by ∼0.12 eV).…”

“…After sulfidation in H 2 S ambiance at 400 °C, the intensities of Mo 3 N 2 peaks decrease. This is concomitant with the evolution of peaks at 2 θ =14.38, 32.68 and 58.34°, which are attributed to MoS 2 (ICSD card No.04‐9801) …”

“…The lower resistance observed in case of Mo 3 N 2 , is reasonable since it is a conductor (unlike MoS 2 which is a semiconductor) . While the value for MoS 2 is >200 Ω. MoS 2 /Mo 3 N 2 clearly offers much lesser impedance and hence operates at much higher efficiency of charge transfer than the pure sulfide MoS 2 phase . However as indicated above, MoS 2 plays a crucial role in the hybrid; it renders exceptional stability for HER operation in acidic medium.…”

“…However, progress in MoS 2 nanoparticles synthesis has been slowed down primarily owing to the complexity of the procedures involved. To date, despite the intrinsic tenability of the material (especially via stoichiometric control, afforded by this system); the conductivity improvements via single‐phase molybdenum disulfide samples have not been satisfactory enough to offer promise for HER electrocatalytic applications . In wake of this, conductivity enhancement for MoS 2 has been pursued primarily via the following two approaches: (i) doping of suitable heteroatoms into the lattice of MoS 2 , and (ii) formation of hybrids by coupling MoS 2 with conductive species .…”

Pore Surface Engineering of Covalent Triazine Frameworks@MoS2 Electrocatalyst for the Hydrogen Evolution Reaction

“…[10][11][12] However, the inherent large band gap of MoS 2 leads to poor electron transport, thus resulting al arge HER overpotential. With cost-effectiveness and high electrocatalytic performance, non-noblem etal molybdenum disulfide (MoS 2 )n anosheets have been extensively investigated as an efficient catalyst in HER.…”