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Hydrogen production from water splitting is a green and efficient technology for storing clean energy. Herein, cerium-incorporated Ni 2 P nanosheets are designed as trifunctional electrocatalysts to generate hydrogen by hydrothermal self-oxidation of surface nickel foam (NF) in pure water to in-situ form Ni(OH) 2 nanosheets, followed by incorporation of Ce and phosphorization. The prepared material exhibits excellent electrocatalytic performance in hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and urea oxidation reaction (UOR). When the current density is 100 mA cm−2, the UOR potential of Ce-Ni 2 P is 1.473 V lower than that in the OER (1.731 V), suggesting a great potential to replace the sluggish OER for overall water splitting. Moreover, the Ce-Ni 2 P/NF can be applied to the electrochemical treatment of real urine electrolysis with similar performance to the urea electrolysis. Such remarkable performance is attributed to the incroporation of Ce with "Ce3+/Ce4+ redox pairs", which can not only provide abundant reactive sites by the charge transfer appearance of defect sites, but also offer an effective buffering space for the pre-oxidation process from Ni2+ to Ni3+. It is thus beneficial for overall water splitting and coupled urea electrolysis, providing a promising candidate for urine wastewater treatment and clean energy production. • Nanosheets are prepared by hydrothermal self-oxidation of NF in pure water. • Ce leads to the lattice distortion of Ce-Ni2P and generates abundant defects. • Such interactions between Ce and Ni2P promote HER and OER/UOR performance. • Ce-Ni2P/NF can be applied for urine wastewater treatment. [ABSTRACT FROM AUTHOR]

We report a novel fabrication of nickel-molybdenum alloy nanorods catalyst for hydrogen evolution reaction (HER), which is prepared by co-deposition of pure nickel and molybdenum in a multisource sputtering system on the surface of Ni foam substrate. The Ni–Mo alloy film exhibits favorable vertical nanorods structure and presents the most efficient activity for HER compared to the film only including one metal element. The remarkably enhanced catalytic activity is attributed to its ordered array geometry as well as the synergistic interaction between Ni and Mo. Meanwhile, the open space within nanorod arrays facilitates the electrolyte penetration and diffusion of ionic species, allowing high utilization efficiency of active species as well as rapidly release of evolved hydrogen gas from the electrode surface. [ABSTRACT FROM AUTHOR]

• 2D interconnected NiTe/NF nanosheets was prepared by one-step hydrothermal method. • Annealing temperatures have an effect on crystal phase change and HER performance. • It leads to a positive shift of the d-band center on non-stoichiometric Ni 2.86 Te 2. • The Ni 2.86 Te 2 /NF exhibits superior HER performance compared to NiTe/NF. The non-stoichiometric Ni 2.86 Te 2 /NF was prepared by hydrothermal method combined with annealing process. Experimental and theoretical results demonstrate that the transition of crystal phase structure from NiTe to Ni 2.86 Te 2 leads to a strong electronic interaction between tellurium and nickel accompanying with the positive shift of the d-band center, resulting in improving the HER activity compared to the NiTe/NF. [Display omitted] It is of great significance to develop low cost, high-efficiency and environment-friendly electrocatalysts for hydrogen evolution reaction (HER) from water splitting. Herein, nickel telluride nanosheets grown on Ni Foam (NF) with three different crystal phases (NiTe, Ni 2.6 Te 2 and Ni 2.86 Te 2) are fabricated by one-step hydrothermal tellurization followed annealing process. The non-stoichiometric Ni 2.86 Te 2 /NF exhibits superior electrocatalytic HER performance compared to the NiTe/NF and Ni 2.6 Te 2 /NF, which is comparable to the state-of-the-art 20 wt% Pt/C catalyst at high current density. The Ni 2.86 Te 2 /NF only requires an overpotential of 348 mV to drive the current density of 200 mA cm−2 in a 1.0 M KOH electrolyte. Similarly, The Ni 2.86 Te 2 /NF delivered current densities of 200 mA cm−2 at the overpotential of 279 mV in 0.5 M H 2 SO 4. Such excellent performance could be ascribed to the fast electron transfer and positive shift of d d-band center from its rich defective effect of crystal phase transition, as well as to the exposure of active sites provided by the two-dimensional nanosheets with large specific surface area. This work provides valuable insights for the rational modulation of the crystal phase on the nickel telluride for catalyzing HER. [ABSTRACT FROM AUTHOR]

Efficient hydrogen production by water electrolysis is primarily restrained by imperfect over-potential and poor reaction dynamics on oxygen evolution reaction (OER). Thermodynamically favourable urea oxidation reaction (UOR) is a class of promising routes for substituting sluggish OER and for coupling with cathodic hydrogen production because of smaller equilibrium potential (0.37 V) than that of OER (1.23 V). Herein, a versatile Ru-NiO/p-Ni catalyst was prepared through in-situ generating nickel hydroxide nanosheets on the surface of ordered porous Ni, then doping low Ru and annealing treatment. The optimized Ru-NiO/p-Ni displayed outstanding activity and stability towards hydrogen evolution reaction (HER), OER and UOR with potentials of −0.13 V, 1.57 V, and 1.39 V at 100 mA cm−2, respectively. Ru-NiO/p-Ni‖Ru-NiO/p-Ni can achieve 100 mA cm−2 in urea-aided water splitting at a voltage of only 1.58 V, which is prominently 170 mV smaller than the voltage of water electrolysis (1.75 V). The excellent electrocatalytic performance is owing to the outstanding inherent activity generated by cooperative effect of Ru and NiO, along with rich defect and active centre of Ru-NiO/p-Ni supplied by the large surface area of 3D porous structure. The formation of more rich Ni active species with a high valence through transport of electrons between Ru and Ni is favourable to promoting the dissociation of urea molecules, eventually improving UOR. Therefore, it can facilitate urea-aided water splitting, which provides a valuable strategy for constructing versatile catalysts for a cathodic energy-efficient hydrogen production coupled with other anodic oxidation reactions. [Display omitted] • Replacing OER with UOR is apparently energy-saving for hydrogen production. • Ru activates NiO nanosheets grown in-situ on porous Ni to obtain more active sites. • Electron transfers of Ru and Ni species significantly promotes HER/OER/UOR. [ABSTRACT FROM AUTHOR]

Herein, a "chimney effect" formed on the interface between the metal oxide and nickel metal for the hydrogen evolution reaction is confirmed by using density functional theory calculations and experimental methods. • A "chimney effect" formed on the interface between the metal oxide and nickel metal for the hydrogen evolution reaction is found. • The "chimney effect" is a result of the interfacial charge transfer between the metal and metal oxide. • The chemical environment around interface makes the neighboring sites be immune to H 2 O* and OH* adsorption but tend to adsorb H* selectively. • The metal oxide/metal interface is beneficial for the smooth adsorption of H* and the easy desorption of H 2 from the catalyst surface. • Experiments further reveal the key role of the amount of chimney, i.e., the interfacial metal atoms, for the excellent HER activity. Precise atomic-level control of composition and geometric structure at the interface between two catalyst components can effectively tune the catalytic properties. Herein, we found a "chimney effect" formed on the interface between the metal oxide and Nickel metal for the hydrogen evolution reaction, using density functional theory calculations and experimental methods. This special chemical environment around the interface leads the neighboring sites to be immune to the H 2 O* and OH* adsorption and to only selectively adsorb H* properly. Meanwhile, it is also beneficial for the smooth adsorption of the reactant (H*) on the interface and the easy desorption of the product (H 2) from the catalyst surface (ΔG H* close to zero). This phenomenon appears similar to a chimney of hydrogen evolution around the metal oxide/metal interface. Such "chimney effect" is a result of the interfacial charge transfer between the metal and metal oxide, and should be the nature of the interface-induced synergistic effect in metal oxide/metal composite catalysts for HER. Experiments further confirm that the catalytic activity of metal oxide/metal composites for HER can be enhanced by increasing the amount of the chimney - the interfacial metal atoms. [ABSTRACT FROM AUTHOR]