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

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 MoS 2 with VGNS, the overpotential is reduced by similar to 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.