Abstract
Downsizing the cell size of honeycomb monoliths to nanoscale would offer high freedom of nanostructure design beyond their capability for broad applications in different fields. However, the microminiaturization of honeycomb monoliths remains a challenge. Here, we report the fabrication of microminiaturized honeycomb monoliths—honeycomb alumina nanoscaffold—and thus as a robust nanostructuring platform to assemble active materials for micro-supercapacitors. The representative honeycomb alumina nanoscaffold with hexagonal cell arrangement and 400 nm inter-cell spacing has an ultrathin but stiff nanoscaffold with only 16 ± 2 nm cell-wall-thickness, resulting in a cell density of 4.65 × 109 cells per square inch, a surface area enhancement factor of 240, and a relative density of 0.0784. These features allow nanoelectrodes based on honeycomb alumina nanoscaffold synergizing both effective ion migration and ample electroactive surface area within limited footprint. A micro-supercapacitor is finally constructed and exhibits record high performance, suggesting the feasibility of the current design for energy storage devices.
Highlights
Downsizing the cell size of honeycomb monoliths to nanoscale would offer high freedom of nanostructure design beyond their capability for broad applications in different fields
The present electrode design based on Honeycomb monoliths (HMs) makes electrochemical devices cumbersome, and the macrostructural channels of HMs require an impractically large amount of electrolytes to fill up all the channels in order to ensure a sufficient contact between the supported electroactive materials and the electrolyte, which is different from gas-phase catalysis applications
The fabrication process begins with the anodization of a surface-nanopatterned aluminum substrate to obtain nanoporous alumina (Al2O3) with a hexagonal cell arrangement and a cell periodicity of 400 nm
Summary
Downsizing the cell size of honeycomb monoliths to nanoscale would offer high freedom of nanostructure design beyond their capability for broad applications in different fields. Most of those nanoelectrodes suffer from the limit of aspect ratio to maintain their highly oriented nature by avoiding the agglomeration since nanowires and nanotubes with high aspect ratio would prefer to form into many dense clusters, and are difficult to simultaneously satisfy both high specific surface area and low ion transport resistance To this end, downsizing the cell size (e.g., channel diameter and cell wall thickness) of the conventional HMs to nanoscale shall be a solution to efficiently address the challenges for extending the application potentials of HMs. the microminiaturization of the HMs encounters technological difficulties in creating exactly parallel and straight nanoscale channels over a large area by all reported HM fabrication approaches whatever in industry or in laboratory, and faces the challenge to guarantee that the microminiaturized HM would hold the similar excellent mechanical stabilities as the conventional HM. The maximum capacitance of the MSC reaches 128 mF cm−2 at a current density of 0.5 mA cm−2, and the peak energy and power densities are 160 μWh cm−2 and 40 mW cm−2, respectively
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