MoS2/NiO heterocatalyst featuring stacking Structures, oxygen Vacancies, and hydrophilic Interfaces for hydrogen production via urea electrolysis

Abstract

Two-dimensional nano-MoS2 holds remarkable potential for widespread use in hydrogen evolution reaction (HER) applications owing to its high catalytic activity, abundant availability, and low cost. However, its electrocatalytic performance is significantly lower than that of Pt-based catalysts necessitating strategies to improve its catalytic activity. We developed an effective strategy for enhancing the HER performance of MoS2 based on the synergistic effect of oxygen vacancies (Ov), heterostructures, and interfacial wettability. In particular, highly graphitized wood-based carbon (GWC) was used as a platform to prepare a hydrophilic/aerophobic MoS2@Ov-NiO-GWC heterocatalyst featuring nanosheet stacking and containing abundant Ov. Consequently, a current density of 10 mA cm−2 and an overpotential of only 77 mV were achieved in a 1 M KOH electrolyte using the prepared catalyst; notably, the overpotential increase was only 1.2 % after continuous operation for 90 h. Density functional theory calculations showed that coupling MoS2 with the Ov-NiO heterointerface increased the exposure of the MoS2 active sites on the heterointerface and accelerated the electron transfer between NiO and the MoS2 interface, considerably enhancing the HER performance. Moreover, an overall urea electrolysis cell assembled using this heterocatalyst demonstrated excellent hydrogen production activity and durability, with current densities of 10 and 100 mA cm−2 at cell voltages of only 1.33 and 1.46 V, respectively. Even after continuous operation for 75 h at a current density of 100 mA cm−2, the cell exhibited a voltage retention rate of 92.8 %. These results demonstrate the potential of this nano-heterocatalyst to efficiently produce hydrogen via overall urea electrolysis.