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Development of low-cost electrocatalysts toward oxygen evolution (OER) and hydrogen evolution reactions (HER) is crucial for large-scale and clean hydrogen production. Cost-effective transition metal oxide-based catalysts are superbly active for OER; however, their applications in catalyzing HER remain challenging due to unsatisfactory activity and intrinsically poor electronic conductivity. Here, we report the synthesis of NiO nanorods (NRs) with abundant oxygen (O) vacancies via a facile cation exchange strategy. Based on the experimental studies and density functional theory calculations, we demonstrate that the chemical and electronic property of NiO NRs is successfully optimized through O-vacancy engineering; the O-vacancies on the surface of NiO NRs remarkably enhance their electronic conduction and promote HER reaction kinetics simultaneously. The resulting NiO NRs exhibit excellent alkaline HER catalytic activity and durability. Furthermore, these specific designed NiO NRs in situ on carbon fiber paper substrates were directly employed as both HER and OER catalysts for overall water splitting, affording better performance than benchmark Pt and RuO 2 catalysts. The successful synthesis of these metal oxides nanomaterials with abundant O-vacancies may pave a new path for rationally fabricating efficient HER/OER bi-functional catalysts. [ABSTRACT FROM AUTHOR]

Exploiting low-cost and high-activity catalysts is crucial for lowering energy consumption for hydrogen evolution reaction (HER). Herein, we reported a pure Nickel catalyst with high activity and long-term stability at a large current density in an alkaline medium. We employed an industrial machining technology, turning processing, to generate Ni-chips, a self-supported catalyst, with mostly close-packed planes exposed and high compressive strain. The close-packed plane and compressive strain jointly lower the d -band center of the nickel catalyst and overcome the excessive adsorption for reactive intermediates. As such, Ni-chip achieves ultralow overpotentials of 70 mV at 10 mA cm−2 and 297 mV at 1000 mA cm−2. Particularly, the catalyst exhibits outstanding stability at high current density (1 A cm−2), after working for one and a half months (ca. 1070 h), the initial current density merely declined by 7.3%. With its remarkable catalytic activity, excellent stability, ease of synthesis, and utilization of metallic scraps, the Ni-chip catalyst may serve as a promising catalyst for industrial applications. Ni-chip catalysts with high compressive strain and predominantly close-packed planes were prepared through turning processing. This combination effectively mitigated the excessive adsorption of *OH and *H on the Ni surface, enabling an ultralow overpotential of 297 mV at 1000 mA cm-2, and excellent stability at 1 A cm-2 for 1070 h, demonstrating potential as an efficient and durable electrocatalyst. [Display omitted] [ABSTRACT FROM AUTHOR]

Water electrolysis for hydrogen production requires highly active and inexpensive catalysts. Herein, we combine ultrasonic impact nanocrystallization (UIN) technology with nital etching method to rapidly prepare highly efficient self-supporting Cu electrode with abundant low-angle grain boundaries. When used as a catalyst for hydrogen evolution reaction (HER), the as-prepared electrode exhibits an overpotential of 353 mV at a current density of 10 mA cm−2, which is about 200 mV lower than that of the blank Cu plate. Moreover, the overpotential decreased to 246 mV after the stability test of 100 h, indicating a self-optimizing property. This work paves a new way for the preparation of self-supporting electrode with high performance. • Ultrasonic impact nanocrystalline could be used in catalysis. • Cu self-supporting electrode with high density surface dislocation is prepared. • The dislocation density could be precisely adjusted by controlling the etching time. • Electrode exhibits high HER activity and stability, shows self-optimized performance. • Dislocations have lower hydrogen adsorption free energies than perfect crystals. [ABSTRACT FROM AUTHOR]

As a cheap and earth-abundant metal, copper is known highly conductive but inactive for catalyzing hydrogen evolution reaction (HER) due to its fully filled d orbital and weak adsorption for hydrogen intermediate. Herein, we adopt a mechanical stirring process to introduce a large number of dislocations into copper plate, and retain the dislocations by the quenching effect of dry ice. Theoretical computation indicates that dislocation can cause uneven distribution of charge density, and the electron-deficient area remarkably enhances the hydrogen adsorption, turning inactive copper into active HER catalyst. The product achieves high turnover frequency, low overpotential and long-term durability. Our work bridges mechanical process and functional materials, and exploits a powerful technology on producing self-supported catalysts in a rapid way : [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: ZnO and TiO2 single-crystalline nanowires (SCNWs) are considered to be ideal materials for the photoanode of dye-sensitized solar cells (DSSCs) due to their superior property of electron transfer, however, a direct comparison between the above two systems has not been made. In the present work, ZnO and TiO2 SCNWs were synthesized directly on conductive glasses by wet chemical methods, and their sizes were kept identical. After being sensitized by N3 dye, the two kinds of nanowires were employed as photoanodes for assembling DSSCs. Comparative studies show that, although TiO2 SCNWs adsorb less dye molecules, they could effectively retard charge recombination and achieve longer electron lifetime than ZnO SCNWs; as a result, the DSSCs composed of TiO2 SCNWs exhibit higher performance than those of ZnO SCNWs. [Copyright &y& Elsevier]

Abstract: Carbon-microtube ring were synthesized by a multi-step template mechanism. Firstly, silica microrings were produced as template by the oxidization of silicon wafer, and then the silica microrings were coated with carbon layers from the decomposed methane. Finally, the silica microrings were removed with hydrofluoric acid, which allows the formation of carbon-microtube rings. [Copyright &y& Elsevier]