Interface Modulation of Two-Dimensional Superlattices for Efficient Overall Water Splitting.

Molecular-scale modulation of interfaces between different unilamellar nanosheets in superlattices is promising for efficient catalytic activities. Here, three kinds of superlattices from alternate restacking of any two of the three unilamellar nanosheets of MoS2, NiFe-layered double hydroxide (NiFe-LDH), and graphene are systematically investigated for electrocatalytic water splitting. The MoS2/NiFe-LDH superlattice exhibits a low overpotential of 210 and 110 mV at 10 mA cm-2 for oxygen evolution reaction (OER) and alkaline hydrogen evolution reaction (HER), respectively, superior than MoS2/graphene and NiFe-LDH/graphene superlattices. High activity and stability toward the overall water splitting are also demonstrated on the MoS2/NiFe-LDH superlattice bifunctional electrocatalyst, outperforming the commercial Pt/C-RuO2 couple. This outstanding performance can be attributed to optimal adsorption energies of both HER and OER intermediates on the MoS2/NiFe-LDH superlattice, which originates from a strong electronic coupling effect at the heterointerfaces. These results herald the interface modulation of superlattices providing a promising approach for designing advanced electrocatalysts.