One‐Step Synthesis of a Coral‐Like Cobalt Iron Oxyhydroxide Porous Nanoarray: An Efficient Catalyst for Oxygen Evolution Reactions

Nickel Sulfide/Hierarchical Porous Carbon from Spent Residue Hydrocracking Catalyst as Electrocatalyst for the Oxygen Evolution Reaction

Spent residue slurry-phase hydrocracking catalyst coated with coke have been classified as hazardous solid waste, presenting serious economic and environmental issues to refiners. Herein, the spent catalysts with a nickel sulfide nanoparticle/coke hierarchical structure (NiSX /C) from our previous work were used to prepare nickel sulfide/hierarchical porous carbon (NiSX /HPC) for the oxygen evolution reaction (OER) through the method of carbonization, activation, and sulfurization. The results indicate that the NiSX /C converts into Ni/HPC after carbonization and activation, and then transform into NiSX /HPC by sulfurization. The optimized NiSX /HPC-8 possesses the crystal phase of NiS2 , and the high specific surface area of 1134.9 m2  g-1 with the hierarchical micro-mesoporous structure. Besides, NiSX /HPC-8 achieves a low overpotential of 236 mV at 10 mA cm-2 , a low Tafel slope of 64.1 mV dec-1 , and excellent stability. This work provides a viable method for upcycling spent catalysts to re-constructed OER catalysts with high catalytic performance and durability.

Construction of hierarchical layered hydroxide grown in situ on carbon tubes derived from a metal-organic framework for asymmetric supercapacitors

Electrode materials are very important for the performance of supercapacitors (SCs). Therefore, preparation of hybrid electrode materials is an effective way to develop high-performance SCs. We firstly design and prepare metal organic framework (MOF) derived carbon nanotubes as the core skeleton to support the shell of a nickel gallium layered hydroxide nanosheet (NiGa-LDH). MOF derived carbon nanomaterials have high conductivity and a large specific surface area, which can promote electron transfer and improve the agglomeration of LDH. The deposited LDH can provide high specific capacitance and the layered structure can further enhance the reaction site. The NiGa-LDH@CNT-500@CC has an excellent specific capacitance of 2580 F g-1 at 1 A g-1 and a high capacitance retention rate of 83.3% at 5 A g-1 due to the synergistic effect of two materials. The assembled NiGa-LDH@CNT-500@CC//carbon NS asymmetric supercapacitor (ASC) has an operating voltage of 1.6 V and a high energy density of 52 W h kg-1 at a power density of 952 W kg-1. Therefore, the core-shell structure composed of LDH and carbon nanomaterials provides an effective way for the design of high-performance electrodes.

An effective approach to achieve high energy storage density and efficiency in BNT-based ceramics by doping AgNbO3

Perovskite dielectric materials for capacitors have received wide attention in recent years because of their fast charge/discharge rates and high power densities. In this work, lead-free relaxor ferroelectric ceramics of (1 -x)[(Bi_0.55Na_0.45)_0.94Ba_0.06]_0.98La_0.02TiO₃-xAgNbO₃ were synthesized by a conventional sintering method. All ceramics are situated at the morphotropic phase boundary (MPB) of rhombohedral and tetragonal phases, suggesting that a small amount of AgNbO₃ (abbreviated as AN) doping does not affect this phase-coexistence structure. The added AN not only improves the dielectric breakdown strength (DBS) from 84.11 kV cm^-1 (x = 0) to 137.89 kV cm^-1 (x = 0.01), but also broadens the phase transition peak and enhances the relaxation behavior of ceramics. Moreover, when x = 0.01, the ceramic demonstrates a high saturation polarization (P_s) of 25.54 μC cm^-2 and a low remanent polarization (P_r) of 0.65 μC cm^-2 at an electric field of 130 kV cm^-1. More importantly, an optimal energy storage density (W_s) of 1.697 J cm^-3 and energy efficiency (η) of 82.3% are simultaneously achieved in the BNBLT-0.01AN ceramic with excellent thermal stability (∼25-175 °C) and frequency stability (∼10-80 Hz).