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The development of economical, efficient, and durable bifunctional catalyst for overall water splitting is an attractive and challenging task. Herein, a novel defect-rich 2D/2D heterostructure is constructed by vertically growing S-doped NiMoO 4 (NiMoO 4 -S) nanosheets on nickel sulfide (Ni 3 S 2) nanosheet arrays supported on nickel foam (NF) using a two-step hydrothermal method. Benefiting from the hierarchical sheet-on-sheet heterogeneous nanostructure and abundant oxygen vacancies for more active sites, efficient electronic/mass transfer, and fast gas release, the synthesized NiMoO 4 -S/Ni 3 S 2 /NF electrode exhibits excellent electrocatalytic performance for HER (η 10 mA cm −2 = 107 mV) and OER (η 50 mA cm −2 = 285 mV). The alkaline water electrolyzer with NiMoO 4 -S/Ni 3 S 2 /NF as the positive and negative electrodes can provide a current density of 10 mA cm−2 with the potential of 1.52 V, which is below that of the commercial Pt||RuO 2 /NF system or many other reported systems. More importantly, the alkaline water electrolyzer offers a current density of 100 mA cm−2 at 1.85 V with outstanding durability of over 50 h. This research points to a promising route in designing transition metal-based bifunctional electrocatalysts for large-scale energy conversion applications. [Display omitted] • A novel defect-rich S-doped NiMoO 4 -S/Ni 3 S 2 2D/2D heterostructures catalyst on nickel foam (NF) was synthesized. • The NiMoO 4 -S/Ni 3 S 2 /NF has a unique sheet-on-sheet structure and abundant oxygen vacancies. • The NiMoO 4 -S/Ni 3 S 2 /NF exhibit superior overall water splitting performance in alkaline media. [ABSTRACT FROM AUTHOR]

ZrN and TiNiN nanolayers are alternately deposited on silicon substrate by magnetron sputtering. A series of ZrN/TiNiN nano-multilayer films with different Ni contents are prepared by varying the Ni:Ti volume ratio of the targets. The effects of Ni content on the microstructures and mechanical properties of ZrN/TiNiN nano-multilayer films are studied by X-ray diffractometer (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and nanoindentation instrument. The results show that with the increase of Ni content, the crystallization degree of ZrN phase first increases and then decreases. Besides, the hardness, elastic modulus and toughness of the films also increase first and then decrease with Ni content increasing. When Ni:Ti= 1:24, the ZrN/TiNiN nano-multilayer films obtain the highest hardness, elastic modulus and fracture toughness, which are 23.2 GPa, 317.8 GPa and 2.29 MPa·m1/2, respectively. This is mainly attributed to the best columnar crystal growth of the ZrN/TiNiN nano-multilayer film. The TiNiN layer changes into face centered cubic structure under the template of ZrN layer, and grows in coherent epitaxy with ZrN layer. ● A series of ZrN/TiNiN nano-multilayer films with different Ni contents are prepared by magnetron sputtering. ● When Ni:Ti= 1:24, the ZrN/TiNiN nano-multilayer films simultaneously obtain the highest hardness and fracture toughness. ● The high hardness and toughness are due to that the TiNiN layer grows in coherent epitaxy under the ZrN layer template. [ABSTRACT FROM AUTHOR]