One-Step Synthesis of Monodispersed Mesoporous Carbon Nanospheres for High-Performance Flexible Quasi-Solid-State Micro-Supercapacitors.

Cost-effective synthesis of carbon nanospheres with a desirable mesoporous network for diversified energy storage applications remains a challenge. Herein, a direct templating strategy is developed to fabricate monodispersed N-doped mesoporous carbon nanospheres (NMCSs) with an average particle size of 100 nm, a pore diameter of 4 nm, and a specific area of 1093 m2 g-1 . Hexadecyl trimethyl ammonium bromide and tetraethyl orthosilicate not only play key roles in the evolution of mesopores but also guide the assembly of phenolic resins to generate carbon nanospheres. Benefiting from the high surface area and optimum mesopore structure, NMCSs deliver a large specific capacitance up to 433 F g-1 in 1 m H2 SO4 . The NMCS electrodes-based symmetric sandwich supercapacitor has an output voltage of 1.4 V in polyvinyl alcohol/H2 SO4 gel electrolyte and delivers an energy density of 10.9 Wh kg-1 at a power density of 14014.5 W kg-1 . Notably, NMCSs can be directly applied through the mask-assisted casting technique by a doctor blade to fabricate micro-supercapacitors. The micro-supercapacitors exhibit excellent mechanical flexibility, long-term stability, and reliable power output.

Catalysts confined inside CNTs derived from 2D metal-organic frameworks for electrolysis.

Two-dimensional metal-organic framework (MOF) nanosheets have attracted considerable research interest as electrocatalysts, and thermal annealing is important to boost their conductivity. The effect of annealing atmosphere on the electrochemical performance of 2D MOFs and their catalytic center structure have been investigated. The Co-MOF/H2 synthesized by annealing of 2D MOF under a H2 atmosphere has shown a significantly enhanced catalytic activity compared with those annealed under an Ar atmosphere (Co-MOF/Ar). The Co-MOF/H2 has 2-3 graphitic layers of graphitic carbon coating and presents a large amount of high valent Co2+. H2 annealing leads to a fast reduction of Co-MOF to Co/CoOx nanoparticles and catalyzes the growth of CNTs with MOF feed as carbon source. The Co-MOF/H2 shows a high electrocatalytic activity which requires an overpotential of 312 mV to reach a current density of 10 mA cm-2. A Co-MOF/H2-based water electrolyzer requires a potential of 1.619 V to reach a current density of 10 mA cm-2 for overall water splitting in 1.0 M KOH. After 25 h of continuous operation for water electrolysis, the Co-MOF/H2-based cell has shown a negligible increase in the overpotential, indicating its superior durability compared to the 2D Co-MOF.