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Molybdenum disulfide (MoS2) nanosheets are promising candidates as earth-abundant and low-cost catalyst for hydrogen evolution reaction (HER). Nevertheless, compared with the benchmark Pt/C catalyst, the application of MoS2 nanosheets is limited to its relatively low catalytic activity, especially in alkaline environments. Here, we developed a dual-cation doping strategy to improve the alkaline HER performance of MoS2 nanosheets. The designed Ni, Co co-doped MoS2 nanosheets can promote the tandem HER steps simultaneously, thus leading to a much enhanced catalytic activity in alkaline solution. Density functional theory calculations revealed the individual roles of Ni and Co dopants in the catalytic process. The doped Ni is uncovered to be the active site for the initial water-cleaving step, while the Co dopant is conducive to the H desorbing by regulating the electronic structure of neighboring edge-S in MoS2. The synergistic effect resulted by the dual-cation doping thus facilitates the tandem HER steps, providing an effective route to raise the catalytic performance of MoS2 materials in alkaline solution. [ABSTRACT FROM AUTHOR]

• 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]

• 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]

Inexpensive metal-based electrocatalyst with excellent stability and activity for efficient hydrogen evolution reaction is the most critical issue for large-scaled water splitting. However, the electricity kinetics in alkaline is relatively sluggish than in acid owing to the concentration of protons in alkaline is low. Thus, accurate structural designs to obtain more protons in the water dissociation on the surface of catalyst are necessary. In this work, a defect-rich MoP is encapsulated with carbon shell, which precisely regulated to distinguish the affection on hydrogen evolution reaction. The synergistic effect between carbon shell and defective sites is identified by the free energy and charge distribution density for water/hydrogen adsorption in hydrogen evolution via a density functional theory calculation. The results show that the lattice defects and the carbon shells play a unique role in enhancing catalytic performance, which the lattice defects decide the active sites and the thinner carbon shell would enhance its activity. The optimal overpotential in alkaline media of this designed MoP/C is 100 mV at 10 mA cm−2, its Tafel slope is 67.4 mV dec−1, and also exhibits a long-term stability for 12 h. • Structure disordering and carbon shell on MoP precisely regulated. • Low onset overpotential (30 mV), small Tafel slope (67.4 mV·dec−1) can achieved in alkaline media. • Synergistic effect between lattice defects and carbon shell are considered to enhance HER catalytic performance. [ABSTRACT FROM AUTHOR]