Herein, we report a micro-mix strategy for the continuous and large-scale synthesis of Ni–Co PBA nanoparticles. The technique presented in this study allows the particle size to be controlled in the 165 nm to 350 nm range while maintaining a high specific surface area (250 m2 g−1) and cubic structure. Furthermore, the particles exhibit superior dispersity and have a more homogeneous particle size than those prepared using the conventional stirring-mix method due to the drastic collisions that occur in the microchannel during the precipitation process. The present study demonstrates that the concentration of raw materials and feed flow rates in the microreactor effectively control the particle size during mixing. The high concentration of raw materials could decrease the particle size, and the particle size is decreased with the increasing feed flow rates when Re (Reynolds number) <783. Particularly, when 783 < Re < 1567, the particle size remains stable (about 165 ± 10 nm). Additionally, the space-time yield (STY) of Ni–Co PBA is 471 kg m−3 d−1. Finally, the continuous flow microreactor can continuously fabricate large-scale and high-quality Ni–Co PBA crystals with distinct morphological features in a short period of time, providing an effective alternative to the time-consuming and multi-step MOF synthesis method.
Engineering hierarchical heterostructure materials has been recognised as a challenging but prepossessing strategy for developing hybrid supercapacitors. Thus, a Ni–Co PBA derived 3D/1D heterostructure NiO/NiCo2O4 based layered double hydroxide on carbon cloth (CC/NiO/NiCo2O4/NiMn-LDH) as a battery-type electrode was successfully designed via a controllable hydrothermal method. The 3D Ni–Co PBA nanocubes served as scaffolds, providing more space for the nickel-cobalt precursors to grow and then calcine to form a continuous conductive layer of 3D/1D CC/NiO/NiCo2O4. Subsequently, 2D ultrathin NiMn-LDH nanosheets were uniformly anchored on 3D/1D NiO/NiCo2O4, resulting in a unique hierarchical structure that effectively addressed the restacking issue and dead volume of NiMn-LDH, contributing to increased charge and electron transport rates, which promoted the reaction kinetics. Benefiting from abundant interfaces with the open channels of the nanoarchitecture, the CC/NiO/NiCo2O4/NiMn-LDH electrode showed an exceptional specific capacity of 1593.0 C g−1 at 1 A g−1 and a desirable rate performance of 92.9% at a current density of 8 A g−1. Surprisingly, HSC devices can achieve an ideal specific energy of 44.28 W h kg−1 at a specific power of 108.22 W kg−1 with 97.59% cycling durability after 10 000 consecutive charge/discharge cycles. These remarkable properties indicate that the designed novel hierarchical heterostructure electrode has great potential for broad applications in electrochemical energy storage systems.
Haiyang Zhai,Jie He,Suili Shi,Mingtang Liu,Zhiliang Jin
A pretreatment method can simultaneously achieve the removal of the surface passivation layer and vacancy engineering. • The difference in work function drives electron injection, resulting in a redistribution of electrons at the interface. • A multi-scale evidence chain verified the vacancy construction and directional charge transfer in a closed-loop manner. • Ion-intercalation pseudocapacitive storage provides high capacitance, wide voltage window, and persistent ASC performance. Owing to sluggish kinetic processes, the development of high-energy-density supercapacitors still faces major challenges. Herein, a NiSe 2 -Vse@Ni-Co PBA heterojunction synthesized through a sodium borohydride (NaBH 4 ) pretreatment-assisted assembly strategy is reported. The novelty of this work lies in the fact that the NaBH 4 treatment simultaneously depassivates the NiSe 2 surface, introduces a high density of selenium vacancies, and weakens the electrostatic repulsion between NiSe 2 and negatively charged Ni-Co PBA, thereby facilitating closer interfacial contact. Electron paramagnetic resonance (EPR) measurements confirm the successful generation of selenium vacancies. Density functional theory (DFT) calculations further reveal a pronounced work-function difference between NiSe 2 and Ni-Co PBA, while selenium vacancies increase the d-orbital states near the Fermi level in NiSe 2 -Vse. Together, these factors favour directional electron donation from the vacancy-rich NiSe 2 side to the PBA side after interfacial contact. Combined with the XPS results, this interfacial electron redistribution is consistent with the partial reduction of Co species and the markedly improved charge-transfer behaviour. As a result, the optimised electrode delivers a high specific capacitance of 1631.14 F g −1 and retains 80.37% of its initial capacitance after 5000 cycles. The assembled asymmetric supercapacitor operates stably at 1.7 V, achieving an energy density of 52.19 Wh kg −1 at a power density of 739.64 W kg −1 , and maintains 78.71% of its initial capacitance after 5500 cycles. This work shows that a simple pretreatment step can integrate surface depassivation, vacancy engineering, and work-function-driven interfacial electron redistribution into a single heterojunction system, offering a practical route to high-performance supercapacitor electrodes. Download: Download high-res image (189KB) Download: Download full-size image
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