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• A composite with MoNi 4 alloys embedding into MoO 3-x porous nanorods was synthesized via a simple in-situ reduction method. • The obtained MoNi 4 @MoO 3-x exhibits a remarkable HER activity with 10 mA/cm2 constant current under 58.6 mV low overpotential. • The remarkable HER activity is found to originate from the MoNi 4 alloys, excellent conductivity and porous structure. [Display omitted] Hydrogen evolution reaction (HER) in alkaline media is expected to become a renewable and economical technology for hydrogen production. Various non-noble electrocatalysts have been explored for HER, in which Ni-Mo alloy is one of the best media. However, its syntheses are complicated and costly. In this work, we contribute an in-situ reduction method of porous MoNi 4 @MoO 3- x nanorods. The synthesized MoNi 4 @MoO 3- x exhibits a remarkable HER activity with 10 mA/cm2 constant current under 58.6 mV extremely low overpotential, small Tafel slope of 44.8 mV/decade, and high durability in 1 M potassium hydroxide electrolyte. Its remarkable activity is found to originate from the highly activity of MoNi 4 , excellent conductivity and favorable porous structure. This work is believed to provide a promising strategy for the HER development of highly active and cost-effective electrocatalysts. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) is a half-cell reaction in water electrolysis for producing hydrogen gas. In industrial water electrolysis, the HER is often conducted in alkaline media to achieve higher stability of the electrode materials. However, the kinetics of the HER in alkaline medium is slow relative to that in acid because of the low concentration of protons in the former. Under the latter conditions, the entire HER process will require additional effort to obtain protons by water dissociation near or on the catalyst surface. Heterostructured catalysts, with fascinating synergistic effects derived from their heterogeneous interfaces, can provide multiple functional sites for the overall reaction process. At present, the activity of the most active known heterostructured catalysts surpasses (platinum-based heterostructures) or approaches (noble-metal-free heterostructures) that of the commercial Pt/C catalyst under alkaline conditions, demonstrating an infusive potential to break through the bottlenecks. This review summarizes the most representative and recent heterostructured HER catalysts for alkaline medium. The basics and principles of the HER under alkaline conditions are first introduced, followed by a discussion of the latest advances in heterostructured catalysts with/without noble-metal-based heterostructures. Special focus is placed on approaches for enhancing the reaction rate by accelerating the Volmer step. This review aims to provide an overview of the current developments in alkaline HER catalysts, as well as the design principles for the future development of heterostructured nano- or micro-sized electrocatalysts. [ABSTRACT FROM AUTHOR]

Searching for a cost-effective, high efficient and stable bifunctional electrocatalyst for overall water-splitting is critical to renewable energy systems. In this study, three-dimensional (3D) curved nanosheets of Mo-doped Ni 3 S 2 grown on nickel foam were successfully synthesized via a one-step hydrothermal process. The hydrogen-evolution reaction (HER) and the oxygen-evolution reaction (OER) in alkaline environment of this 3D catalyst are investigated in detail. The results show that it possesses lower overpotential, high current densities and small Tafel slopes both in OER and HER. For HER, the catalysts show excellent electrochemical performance, demonstrating a low over-potential of 212 mV at 10 mA cm −2 with a large decrease of 127 mV compared to the undoped Ni 3 S 2 . And it also shows a lower overpotential of 260 mV at 10 mA cm −2 which decreases 30 mV for OER. In addition, it is only need 1.67 V for the overall water splitting at 10 mA cm −2 which is 70 mV. It found that the Mo element would change the morphology of Ni 3 S 2 and induce much more active sites for HER and OER. The as-prepared Mo-doped Ni 3 S 2 bi-functional electrocatalyst could act as the promising electrode materials for water splitting. [ABSTRACT FROM AUTHOR]

• A novel 3D core-shell structed catalyst with metallic Mo-Ni nanoparticles was constructed. • The introduced Mo-Ni would make NiFe LDH nanosheets uniformly growth and provide a rapidly electron transfer channel. • The electrochemistry of 134 mV, 278 mV and 1.64 V (HER, OER, overall water splitting) at 100 mA cm–2 can achieve. It is still a great challenge to develop efficient and stable monolithic electrocatalysts with effective cost and abundant natural resources. Herein, a 3D structured NiFe layered double hydroxide (NiFeLDH) nanosheets rationally decorated on MoNi/NiMoO x nanowires array supported on Ni foam (MoNi/NiMoO x @NiFe LDH) are fabricated by an in-situ growth process is firstly reported. The results show that MoNi alloys can build a fast electron transport channel, thus improving the efficiency of the electrocatalyst. And the ultrathin NiFe LDH nanosheets would provide abundant exposed defects and catalytic active sites. A low overpotential (278 mV at 100 mA cm−2) and Tafel slope (44.7 mV dec−1) for oxygen evolution reaction, and overpotential (134 mV at 100 mA cm−2) and Tafel slope of 81.0 mV dec−1 for hydrogen evolution reaction in 1 M KOH can achieved. The overall water splitting system composed with 3D core–shell catalyst (MoNi/NiMoO x @NiFe LDH) and MoNi/NiMoO x nanowire arrays, which can obtain 100 mA cm−2 at a voltage of 1.64V, even superior to the benchmark of IrO 2 (+) // Pt/C (-). Image, graphical abstract [ABSTRACT FROM AUTHOR]