Electrochemical or photoelectrochemical water splitting is an environmentally friendly technology for H2 production to replace fossil fuels for industrial and social utilization of energy. Metallic transition-metal dichalcogenide (TMDC) nanomaterials are significantly promising for applications in practical catalysis of water splitting to replace state-of-the-art noble-metal-based catalysts. High intrinsic activity and remarkable conductivity are the main advantages of these materials. Structural and compositional design can also be used to improve the catalytic performance.

Highly active and robust eletcrocatalysts based on earth-abundant elements are desirable to generate hydrogen and oxygen as fuels from water sustainably to replace noble metal materials. Here we report an approach to synthesize porous hybrid nanostructures combining amorphous nickel-cobalt complexes with 1T phase molybdenum disulfide (MoS₂) via hydrazine-induced phase transformation for water splitting. The hybrid nanostructures exhibit overpotentials of 70 mV for hydrogen evolution and 235 mV for oxygen evolution at 10 mA cm^-2 with long-term stability, which have superior kinetics for hydrogen- and oxygen-evolution with Tafel slope values of 38.1 and 45.7 mV dec^-1. Moreover, we achieve 10 mA cm^-2 at a low voltage of 1.44 V for 48 h in basic media for overall water splitting. We propose that such performance is likely due to the complete transformation of MoS₂ to metallic 1T phase, high porosity and stabilization effect of nickel-cobalt complexes on 1T phase MoS₂.

Great attention has been focused on the design of electrocatalysts to enable electrochemical water splitting-a technology that allows energy derived from renewable resources to be stored in readily accessible and non-polluting chemical fuels. Herein we report a bifunctional nanotube-array electrode for water splitting in alkaline electrolyte. The electrode requires the overpotentials of 58 mV and 184 mV for hydrogen and oxygen evolution reactions respectively, meanwhile maintaining remarkable long-term durability. The prominent performance is due to the systematic optimization of chemical composition and geometric structure principally-that is, abundant electrocatalytic active sites, excellent conductivity of metallic 1T' MoS₂, synergistic effects among iron, cobalt, nickel ions, and the superaerophobicity of electrode surface for fast mass transfer. The electrode is also demonstrated to function as anode and cathode, simultaneously, delivering 10 mA cm^-2 at a cell voltage of 1.429 V. Our results demonstrate substantial improvement in the design of high-efficiency electrodes for water electrolysis.