One-step hydrothermal synthesis of a Ni 3 S 2 -FeMoO 4 nanowire-nanosheet heterostructure array for synergistically boosted oxygen evolution reaction.

A key factor for boosting oxygen evolution reaction (OER) is the design of heterostructures with steerable defects and interfaces, which can optimize the surface electronic structures and achieve efficient water splitting to produce hydrogen fuel. Herein, we propose a novel one-step hydrothermal approach to fabricate hierarchical Ni 3 S 2 nanowires with an S-doped FeMoO 4 nanosheet heterostructure array in situ on Ni-Fe foam (NFF) as a self-standing electrode for synergistically boosted OER. The metalloid Ni 3 S 2 nanowires with good conductivity support the FeMoO 4 nanosheets and act as high-speed paths for the charge transfer. Numerous ultrathin S-doped FeMoO 4 nanosheets are uniformly distributed on each Ni 3 S 2 nanowire to form heterostructures with larger specific surface area and more revealable active sites, and a strong synergistic effect is created at the heterostructure interfaces to further promote the OER dynamics. Additionally, the NFF serves as the conductive support substrate and simultaneously provides the Ni and Fe sources for the self-growing Ni 3 S 2 -FeMoO 4 , leading to a structurally-integrated electrode with low contact resistance, fast mass transfer, and good stability. Therefore, the Ni 3 S 2 -FeMoO 4 /NFF electrode offers a low overpotential of 331 mV to achieve 500 mA cm -2 and long-term stability at 100 mA cm -2 level for more than 40 h. This work provides insight into the heterostructure of molybdate and sulfide, and a deep understanding of the significance of the synergism in OER operation.