Thermal self-reduction of metal hydroxide acrylate monolayer nanoparticles leads formation of nanoparticulate and porous structured alloys

Chemical and physical designs of alloy nanomaterials have attracted considerable attention for the development of highly functional materials. Although polyol processes using ionic precursors are widely used to synthesise alloy nanoparticles, the reduction potential of polyols limits their chemical composition, making it difficult to obtain 3d transition metals. In this study, we employed pre-synthesized metal hydroxide salt monolayer nanoparticles as precursors to obtain alloy nanoparticles. Simultaneous dehydroxylation of the hydroxide moiety and decomposition of the organic moiety allowed the formation of stable face-centred cubic metals passing through the metal carbide and metastable hexagonal close-packed metal phases. This self-reduction process enabled the formation of nanoparticulate bimetallic alloys and macroporous/mesoporous-structured bimetallic alloys by compositing hard/soft templates with pre-synthesized metal hydroxide salt nanoparticles. We believe that the strategy presented in this study can be used to design nanostructures and chemical compositions of multimetallic alloy nanoparticles as well as bimetallic systems.

Thermal Conversion of Nanocrystalline Metal Hydroxide Salts to Metal Carbides, Pnictides, Chalcogenides, and Halides

A general procedure for synthesizing various inorganic compounds in a similar manner is required in the field of material chemistry. The use of solid-state reactive agents with inorganic precursors is a successful approach in this direction. In this study, organic-inorganic hybrid metal hydroxide salts (MHSs) were utilized to synthesize various inorganic compounds by a simple heat treatment method because they can be assumed to be "premixed" inorganic precursors and solid-state reactive agents. Comparative studies revealed that the nanocrystalline characteristics and coordination of the carboxylate of the synthesized MHSs enabled simultaneous dehydration of hydroxides and decomposition of carboxylates and subsequent formation of metals and metal sulfides. Manganese, iron, cobalt, nickel, and zinc sulfides, as well as nickel carbides, pnictides, chalcogenides, and halides were obtained using the same procedure. We believe that using nanocrystalline organic-inorganic hybrid MHSs as both inorganic precursors and organic reactive agents will be a simple and versatile way to prepare a wide variety of inorganic complex compounds.

The Effect of Lithium Ion Leaching from Calcined Li-Al Hydrotalcite on the Rapid Removal of Ni2+/Cu2+ from Contaminated Aqueous Solutions

A layered double hydroxide (LDH) calcined-framework adsorbent was investigated for the rapid removal of heavy metal cations from plating wastewater. Li-Al-CO₃ LDH was synthesized on an aluminum lathe waste frame surface to prepare the sorbent. The calcination treatment modified the LDH surface properties, such as the hydrophilicity and the surface pH. The change in surface functional groups and the leaching of lithium ions affected the surface properties and the adsorption capacity of the heavy metal cations. A zeta potential analysis confirmed that the 400 °C calcination changed the LDH surface from positively charged (+10 mV) to negatively charged (-17 mV). This negatively charged surface contributed to the sorbent instantly bonding with heavy metal cations in large quantities, as occurs during contact with wastewater. The adsorption isotherms could be fitted using the Freundlich model. The pseudo-second-order model and the rate-controlled liquid-film diffusion model successfully simulated the adsorption kinetics, suggesting that the critical adsorption step was a heterogeneous surface reaction. This study also confirmed that the recovered nickel and/or copper species could be converted into supported metal nanoparticles with a high-temperature hydrogen reduction treatment, which could be reused as catalysts.

Formation of double-cone-shaped ZnO mesocrystals by addition of ethylene glycol to ZnO dissolved choline chloride–urea deep eutectic solvents and observation of their manners of growth

ZnO mesocrystals were grown in ZnO dissolved CU-DESs with addition of ethylene glycol. Their manner of growth was observed and discussed.

Development of high-utilization honeycomb-like α-Ni(OH)2 for asymmetric supercapacitors with excellent capacitance

The low utilization rate of active materials has been a critical obstacle for the industrialization of ultracapacitors. In this study, a thin layer of cross-structured ultrathin α-Ni(OH)₂ nanosheets was successfully grown in situ on the surface of a nickel foam as a high-conductivity framework by a vibratory water bath route under a low temperature (80 °C) and mild conditions. Combining the ultrathin α-Ni(OH)₂ nanosheets and ultrashort electron transport, the strategy of a perfect intercalation structure of α-Ni(OH)₂ and a thin layer of active material on a continuous conductive framework resulted in a high utilization rate of active material, which further achieved high specific capacitance of 213.55 F g⁻¹ at 1 A g⁻¹ in a two-electrode system and high capacitance retention from three to two electrode system (753.79 F g⁻¹ at 1 A g⁻¹ in the three-electrode system). Meanwhile, the device also achieved high energy density of 74.94 W h kg⁻¹ at power density of 197.4 W kg⁻¹ and still retained 24.87 W h kg⁻¹ at power density of 3642 W kg⁻¹.

The low utilization rate of active materials has been a critical obstacle for the industrialization of ultracapacitors.

NiZn double hydroxide nanosheet-anchored nitrogen-doped graphene enriched with the γ-NiOOH phase as an activity modulated water oxidation electrocatalyst

Herein, we report a facile solvothermal process to synthesize an active electrocatalyst for the oxygen evolution reaction (OER) in an alkaline medium by anchoring nanosheets of a NiZn double hydroxide over nitrogen doped reduced graphene oxide after enriching the system with the γ-NiOOH phase. This catalyst possesses a thin, porous and open layered structure, which makes the system more efficient and accessible for a better electrochemical water oxidation reaction. Moreover, we experimentally demonstrated that incorporation of Zn via a single-step solvothermal method provides an easy approach to obtain plenty of exposed γ-NiOOH phases to make the system more viable for OER with a small overpotential of 290 mV at 10 mA cm^-2 and a Tafel slope of 44 mV per decade. In addition to this, the oxophilic nature of Zn in the (Zn)Ni-LDH/N-rGO catalyst helps to improve the long-term stability of the whole system. The obtained results open up possibilities for the design of future robust OER electrocatalysts by the use of very cheap and abundant materials like Ni and Zn in place of expensive Ir and Ru in the present commercial electrocatalysts.

Influence of microwave power on the preparation of NiO nanoflakes for enhanced magnetic and supercapacitor applications

Nanoflake-structured NiO were synthesized by a microwave assisted method without the use of additives.