Nanohybridization of MoS₂ with Layered Double Hydroxides Efficiently Synergizes the Hydrogen Evolution in Alkaline Media

SUMMARY

Hydrogen evolution reaction (HER) on earth-abundant molybdenum disulfide (MoS₂) in acidic media is a robust process, but is kinetically retarded in alkaline media. Thus, improving the sluggish kinetics for HER in alkaline media is crucial for advancing the performance of water-alkali electrolyzers. Here, we demonstrate a dramatic enhancement of HER kinetics in base by judiciously hybridizing vertical MoS₂ sheets with another earth-abundant material, layered double hydroxide (LDH). The resultant MoS₂/NiCo-LDH hybrid exhibits an extremely low HER overpotential of 78 mV at 10 mA/cm² and a low Tafel slope of 76.6 mV/dec in 1 M KOH solution. At the current density of 20 mA/cm² or even higher, the MoS₂/NiCo-LDH composite can operate without degradation for 48 hr. This work not only brought forth a cost-effective and robust electrocatalyst, but more generally opened up new vistas for developing high-performance electrocatalysts in unfavorable media recalcitrant to conventional catalyst design.

Context & Scale

Central to electrocatalysis are efficient and robust electrocatalysts composed of earth-abundant elements, which are urgently needed for realizing low-cost and high-performance energy conversion devices. Earth-abundant MoS₂ has emerged as a promising hydrogen evolution reaction (HER) catalyst with high activity and durability. However, such a high HER performance is only limited to acidic media, the kinetics becoming rather sluggish in alkaline media. Besides the hydrogen (H_ad) adsorption energy, there should be a second descriptor for gauging the HER catalytic activity in alkaline media, namely the binding of hydroxyl species, because here H has to be discharged from water instead of from hydronium ions in acidic media. This work is the first to successfully design and fabricate a synergistic hybrid catalyst system, which is composed of MoS₂ as an H-acceptor and OER-efficient layered double hydroxide as an OH acceptor, for dramatically facilitating the HER process in alkaline media. This work is the first to successfully design and fabricate a synergistic hybrid catalyst system, which is composed of MoS₂ as an H-acceptor and OER-efficient layered double hydroxide as an OH acceptor, for dramatically facilitating the rate-determining water dissociation step and thus the overall HER catalysis in alkaline media.