Molybdenum Sulfide for Hydrogen Evolution Reaction: The Importance of Solution Dynamic Wetting Behavior in The Drying...

MoS_x serving as a hydrogen evolution reaction electrocatalyst is known for its morphology sensitive characteristic. The low temperature thermo-decomposition method provides an easy and energy saving pathway to produce highly active MoS_x on carbon paper substrates. However, during the precursor solution drying process, the dynamics of liquid wetting behavior dominates the morphology of the precursor salt and eventually the morphology of MoS_x. As a result, here, for the first time, by carefully pairing the substrate hydrophobicity and solvent polarity, the cohesive force between solvent molecules and adhesive force between solvent and carbon substrate can be tuned, and thus the MoS_x morphology can be controlled. Pairing hydrophilic carbon paper with DMF + H₂O mixing solvent results in a relatively strong adhesive force, as a result, we are able to lower the overpotential required at the benchmark current density, 10 mA/cm², to as low as 0.160 V and boost the current density to 40 mA/cm² at -0.2 V vs RHE. This mainly results from the low charge transfer resistance and the well wrapped MoS_x on carbon paper fiber structure. Furthermore, this well wrapped MoS_x on hydrophilic carbon paper was proved to be comparably stable for constant voltage electrolysis operation.