Kirkendall Effect in Creating Three-Dimensional Metal Catalysts for Hierarchically Porous Ultrathin Graphite with Unique Properties

Abstract

In this work, we report an innovative mechanism, the Kirkendall effect, in creating three-dimensional (3D) microporous catalysts with tunable pore sizes for the growth of hierarchic ultrathin graphite foams (HP-UGFs) with unique properties. Employing the Kirkendall effect is one of the first demonstrated for fabricating 3D porous catalysts, where tunable pores of 1.9–8.3 μm are created on 3D interconnected struts (∼100 μm). With the catalysts, we readily synthesized freestanding HP-UGFs that offer higher crystallinity and electric conductivity, larger surface area, as well as enhanced electric invariance to strains compared to those of conventional ultrathin graphite foams. A gauge factor as low as ∼10 at a strain as high as 80% is achieved owing to the unique porous corrugations created on the microstruts of the HP-UGFs. This work may inspire a new paradigm in designing and synthesizing a new type of 3D porous architecture made of 2D materials with controlled local corrugations, which could greatly benefit flexible electronics.

Synergistic High‐Rate Solar Steaming and Mercury Removal with MoS2/C @ Polyurethane Composite Sponges

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Ultralight and Binder‐Free All‐Solid‐State Flexible Supercapacitors for Powering Wearable Strain Sensors

“…The fabrication of the unique MPGMs started with the synthesis of MPG by using strategically designed 3D copper–nickel (Cu–Ni) foams as catalysts. The multilevel porous Cu–Ni foams were grown by electrodeposition of a uniform thin layer of Cu on struts of Ni foams (MTI Corporation, CA, USA) followed by annealing and then controlled electrochemical etching . Leveraging the distinct migration speed of Cu and Ni atoms at a high temperature, the so‐called Kirkendall effect, dense micropores of 1.9–8.3 µm could be created under the surface of the struts (feature size of 100 µm) by varying the reaction conditions of annealing temperature from 1000 to 1100 °C, annealing time from 5 to 30 min, and Cu deposition from 800 to 2400 Coulombs.…”

Flexible All‐Solid‐State Supercapacitors of High Areal Capacitance Enabled by Porous Graphite Foams with Diverging Microtubes

“…excellent electrical conductivity, outstanding mechanical strength, and high thermal conductivity, but also offer 3D interconnected networks with high porosity, large surface area, and exceptional mechanical durability. [1][2][3][4][5] Two major approaches have been developed to fabricate 3D GFs: (1) solution based synthesis via graphene oxide (GO) reduction and assembly, and (2) template-assisted chemical vapor deposition (CVD). [3,[5][6][7][8][9][10][11] In contrast to those obtained from GO sheets, 3D GFs fabricated by CVD offer superior electrical and mechanical durability owing to high crystalline quality and continuous architectures.…”

“…The fabrication strategy and the obtained materials are reported for the first time. Arrays of graphitic microtubes (2)(3)(4)(5) µm in width, ~30 µm in length) covalently grown on porous graphite can be obtained with high uniformity and reproducibility. They fully fill in the large interspace of ~100-200 µm between graphitic struts of conventional 3D GFs, which readily boosts the volumetric surface area by three times and enables a doubled loading of pseudocapacitive materials (Mn 3 O 4 , 3.91 mg cm -2 ,78 wt%), compared to those of conventional GFs.…”