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Abstract: The growth of CuO nanosheet arrays on Cu foil was demonstrated. The morphology and structure of the CuO were examined by scanning electron microscopy and X-ray diffraction spectroscopy. The catalytic performance of the obtained CuO/Cu electrode for hydrogen peroxide electroreduction in 3.0moldm−3 KOH was evaluated by means of cyclic voltammetry and chronoamperometry. The CuO/Cu electrode shows an onset potential for H2O2 electroreduction comparable to Co3O4 nanowire arrays grown on Ni foam and around 100mV more negative than precious metal catalysts, such as Pt and Pd, demonstrating its good catalytic activity for H2O2 electroreduction. The stabilized mass current density for H2O2 electroreduction on the CuO/Cu electrode at −0.3V reached about 57% of that on Co3O4 nanowire arrays grown on nickel foam. Compared to conventional fuel cell electrodes fabricated by mixing active materials with conducting agents and polymer binders, this electrode of CuO nanosheet arrays directly grown on Cu has superior mass transport property, which combining with its low-cost and facile preparation, make it a promising electrode for fuel cell using H2O2 as the oxidant. [Copyright &y& Elsevier]

The adoption of effective, minimal, and versatile electrocatalysts for water splitting to generate hydrogen fuels is of critical importance. The bulk of newly described materials have considerable onset potential, but their electrocatalytic activity is limited by weak electrical conductivity and a limited range of catalytic sites. The combination of a few precious metals added with transition metal-based compounds is a novel and captivating approach. Herein, cobalt ferrite oxide (Co 2 FeO 4) @ palladium oxide (PdO) nanostructures have been prepared through the combined use of hydrothermal and ultraviolet (UV) irradiation techniques. For hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics, the modified composition offers a high concentration of active sites, improved electrical conductivity, and stability. The Co, Fe, and Pd ions at the composite system's interface may affect the adsorption energy of reaction intermediates synergistically, enabling the process to continue with less potential. The electrocatalyst Co 2 FeO 4 @PdO demonstrates an excellent bifunctional approach to electrochemical water splitting (EWS) for HER and OER in alkaline medium. As-prepared electrocatalyst shows an overpotential value of 269 and 259 mV for HER and OER at 10 and 20 mA/cm2 current densities respectively. The low charge transfer resistance values such as 72.2 and 62.4 Ω and durability for 48 h has been observed toward HER and OER , support this material as an efficient and durable electrocatalyst for energy conversion systems. [Display omitted] • Effective Cobalt–Iron-Ferrite oxides and Palladium-oxide based bifunctional electrocatalyst. • Promising activity for HER and OER with lower Tafel slope values in the alkaline media. • Longer stability and durability for 20 h. [ABSTRACT FROM AUTHOR]

Integrating transition metal complexes with carbon-based materials, especially graphene, is a useful strategy for synthesizing effective hydrogen evolution catalysts. Herein, we report a design of hollow hexagonal NiSe–Ni 3 Se 2 nanosheets grown on reduced graphene oxide (NiSe–Ni 3 Se 2 /rGO) by a simple hydrothermal method as an effective catalyst for hydrogen evolution reaction (HER) in the full pH range. In 0.5 M H 2 SO 4 , the NiSe–Ni 3 Se 2 /rGO possesses 112 mV to achieve 10 mA cm−2 and a small Tafel slope (61 mV dec−1). In 1.0 M PBS and 1.0 M KOH, the overpotentials are 261 and 188 mV at 10 mA cm−2, and Tafel slopes are 103 and 92 mV dec−1, respectively. Meanwhile, it owns good cycle stability and durability over 20 h in the whole pH range (0-14). In all solutions, the HER performance of NiSe–Ni 3 Se 2 /rGO is better than that of NiSe–Ni 3 Se 2. This is because the rGO substrate accelerates the electron transfer and improves the electrical conductivity, increasing HER activity of catalyst. • The hollow hexagonal NiSe-Ni3Se2 nanosheets uniformly decorate the rGO. • The hollow structure exposes more active sites and transport pathways. • The hybrid material exhibits superior performance for HER in all pH media. • The stability of the composite is good under a variety of pH conditions. [ABSTRACT FROM AUTHOR]

Seeking the efficient and robust electrocatalysts necessarily enhances performance of hydrogen evolution reaction (HER). Increasing the surface active sites is a means to improve the performance. Herein, we use the Ni 0·85 Se anchored on reduction of graphene oxide (Ni 0·85 Se/rGO) hybrid material skillfully established by one-step facile hydrothermal method as a robust and stable electrocatalyst applying to hydrogen evolution reaction (HER). In terms of morphology, Ni 0·85 Se nanospheres composed of many nanosheets are uniformly distributed on the graphene sheet layer. We also detailedly analyze its properties. Based on the interaction between Ni 0·85 Se and rGO, and the roles of graphene are as a substrate to heighten conductivity, possesses more active surface area by limiting growth of Ni 0·85 Se, and increases dispersion for exposing more active surface area and enlarge ion/electron transfer rate. In HER, the Ni 0·85 Se/rGO catalyst displays the overpotential of 128 mV with a common current density of 10 mA cm−2, a small Tafel slope of 91 mV dec−1, an extremely low onset potential of 37 mV, outstanding stability that a high current retention of 97.7% after 1000 cycles and well long-term stability for 18 h, outperforming the capability of Ni 0·85 Se nanospheres in alkaline solution for HER. The above results indicate that the Ni 0·85 Se/rGO hybrid material is a good HER ability and non-noble metal electrocatalyst has potential value in HER. • The Ni 0.85 Se nanospheres uniformly decorate the rGO sheets. • The Ni 0.85 Se/rGO electrocatalyst possesses more active surface area. • The stability of the composites can reach 97.7%. • The hybrid material exhibits superior performance for HER. [ABSTRACT FROM AUTHOR]

Porous Ni 2 P nanoflower supported on nickel foam (Ni 2 P@Ni foam) electrodes are synthesized via a simple hydrothermal growth strategy accompanied with further phosphating treatment. The prepared electrodes are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). Electro-catalytic performances towards urea electro-oxidation are tested by cyclic voltammetry (CV), chronoamperometry (CA) coupled with electrochemical impedance spectroscopy (EIS). By phosphating Ni(OH) 2 precursor, the final obtained Ni 2 P@Ni foam electrode presents a porous Ni 2 P nanoflower structure within abundant porosity, and so exposes a large amount of electro-catalytic active sites and electronic transmission channels to accelerate the interfacial reaction. Compared with Ni(OH) 2 @Ni foam precursor, the Ni 2 P@Ni foam catalyst exhibits more excellent electro-catalytic activity as well as lower onset oxidation potential. Remarkably, the Ni 2 P@Ni foam catalyst reaches a peak current density of 750 mA cm −2 with an onset oxidation potential of 0.24 V (vs. Ag/AgCl) accompanied by an excellent stability in 0.60 M urea with 5.00 M KOH solutions. Benefiting from the unique porous nanosheet structure, the as-synthesized Ni 2 P@Ni foam catalyst performs a highly enhanced catalytic behavior for alkaline urea electro-oxidation, indicating that the material can be hopefully applied in direct urea fuel cells. [ABSTRACT FROM AUTHOR]