Modulating Schottky Barrier of MoS₂ to Enhance Hydrogen Evolution Reaction Activity by Incorporating with Vertical Graphene Nanosheets Derived from Organic Liquid Waste

Abstract

The lack of theoretical understanding of the reaction kinetics and the overall electrochemical system of the hydrogen evolution reaction (HER) is the major bottleneck for the design of highly efficient electrocatalysts. Here, we demonstrate that the current barrier between catalyst and current collector is strongly influencing the kinetic activation barrier at the catalyst‐electrolyte interface, and thus, equally important for the overall HER activity. Modulating the current collector/catalyst interface via introducing a layer of vertical graphene nanosheets (VGNS) derived from organic liquid waste is proposed as a feasible modification to lower the current barrier, while applying the concept of waste valorization. Benefiting from the intrinsically good electronic conductivity and low contact resistance at heterojunctions, VGNS plays an effective role in modulating the Schottky barrier contact to enhance HER activity. The enhancing effect is investigated by combining characterization, electrochemical measurements and density functional theory (DFT) calculation. By incorporating MoS2 with VGNS, the overpotential is reduced by ∼50 mV with a Tafel slope of 38 mV per decade. This is in accordance with the reduction of Schottky barrier height (SBH) from 0.52 to 0.23 eV in the model. Our results provide a new perspective into the role of Schottky barrier (contact resistance) on the activity origin of HER, which facilitates to establish a rational guidance for optimizing future electrocatalysts.

Waste-Derived Catalysts for Water Electrolysis: Circular Economy-Driven Sustainable Green Hydrogen Energy

“…Interestingly, the rich pyridinic-N in the carbon support provides additional electroactive sites, and there is a positive correlation between HER performance and the content of N dopant. The critical role of the carbon support in enhancing MoS 2 catalysts' HER performance is also identified in the organic liquid waste-derived vertical graphene nanosheets (VGNS)/ MoS 2 hybrid [132]. By combining VGNS with MoS 2 , the Schottky barrier height is reduced from 0.52 to 0.23 eV in the computational model, which is in line with the experimentally reduced overpotential by ∼ 50 mV.…”

Edge‐Rich Reduced Graphene Oxide Embedded in Silica‐Based Laminated Ceramic Composites for Efficient and Robust Electrocatalytic Hydrogen Evolution

“…In summary, we have developed the rGO/SiO 2 composites as an effective and robust HER electrocatalyst via intercalation and pressure sintering. When compared with previously reported graphene‐based structures, such as heteroatom‐doped graphene, [ 14–16 ] edge‐rich vertical graphene, [ 24,42 ] and graphene‐based heterostructures, [ 28,29 ] or composites, [ 32 ] the proposed self‐supported rGO/SiO 2 composites containing abundant rGO edges showed overwhelming advantages regarding the electrocatalytic activity as well as chemical and mechanical stability ( Figure and Table S2, Supporting Information). On the one hand, the preferred orientation and uniform dispersion of the rGO sheets in the SiO 2 matrix resulted in the exposure of electrocatalytic active edges and the improvement of electrical conductivity.…”

“…Comparison of the electrocatalytic activity of the rGO/SiO 2 bulk composites with previously reported carbon structures [ 14–16,28,32,42 ] for HER in acidic media.…”

Waste to wealth: direct utilization of spent materials for electrocatalysis and energy storage

“…The incorporation of MoS 2 into VGNS led to a dramatically reduced energy gap between the Fermi level and the conduction band minimum (CBM) of MoS 2 , offering prominent HER activity with a reduction of overpotential by 50 mV and a Tafel slope of 38 mV dec −1 . 65 In addition, industrial waste contains large amounts of metals can be used as a metal precursor to form a NiCoMn layered triple hydroxide (LTH) with a hierarchical nanoflower structure by the electrodeposition method. The electrocatalyst exhibited high activity for both OER and HER due to its hierarchical structure and high metal content of 67.33%.…”