Controlling surface porosity of graphene-based printed aerogels

Abstract

The surface porosity of graphene-based aerogels strongly influences their performance in applications involving mass transfer. However, the factors determining the surface porosities are not well-understood, hindering their application-specific optimisation. Here, through experiments and hydrodynamic simulations, we show that the high shear stress during the graphene-based aerogel fabrication process via 3D printing leads to a non-porous surface. Conversely, crosslinking of the sheets hinders flake alignment caused by shearing, resulting in a porous surface. Our findings enable fine control of surface porosity of printed graphene-oxide aerogels (GOA) through regulation of the crosslinking agents and shear stress. Using this strategy, we demonstrate the performance advantages of GOA with porous surface over their non-porous counterpart in dye adsorption, underscoring the importance of surface porosity in certain application scenarios.

Real-time, noise and drift resilient formaldehyde sensing at room temperature with aerogel filaments

“…While the filament diameter simply scales with the nozzle diameter, tuning surface porosity is more complicated. On the basis of our previous study ( 25 ), the surface porosity of printed aerogels is simultaneously controlled by the inks’ crosslinking degree and the shear stress during printing. In principle, printing with a nozzle of smaller diameter at a higher flow rate will result in higher shear stress in the printing nozzle and smaller surface porosity in printed filaments.…”

“…This can be attributed to the decrease in effective diffusion coefficient for filaments with lower surface porosity. Higher surface tension during printing promotes the alignment of flakes near the surface, leading to reduced surface porosity and increased tortuosity ( 25 , 36 ). Consequently, this combination results in a lower effective diffusion coefficient.…”

“…The surface of chemically inert three-dimensional (3D) porous graphene or reduced graphene oxide (rGO) requires appropriate sensitization with other materials such as 0D MOS quantum dots (QDs) to absorb fast-diffusing gas molecules. Crucially, the rational design of the pores and skeleton structures of aerogels are critical for optimized sensor sensitivity, adsorption and desorption dynamics, and detection efficiency ( 25 , 26 ). 3D printing allows engineering and fine-tuning the aerogel structures on multiple scales, providing additional dimensions for extracting dynamic and distinguishable features that are more resilient to noise and baseline drift, widely prevalent in gas sensors.…”

Universal Murray’s law for optimised fluid transport in synthetic structures

“…Graphene oxide aerogels are fabricated according to our previously reported method 51 . First, GO dispersion of 25 mg mL −1 concentration is prepared by mixing non-exfoliated GO paste (Sigma-Aldrich) in DI water and stirring for 4 h. The dispersion is then mixed with 160 mM ascorbic acid (Acros Organics) and heated at 60 ° C for 1 h to gelate the dispersion through the partial reduction of GO 51 . The as-prepared viscous ink is next extruded into 3D-printed PLA moulds to control the shape of the final samples.…”

Sub-mm3 dimensional scaling of fully-integrated additively-fabricated microsupercapacitors for embedded energy storage applications

“…54,55 Thus, due to higher shear stresses at the walls of the nozzles with smaller diameters, the graphitic sheets align more strongly along the printing direction resulting in lower surface roughness/porosity at the outmost surface of the printed electrodes. 56 For the same reason, lower shear stresses are experienced by the graphitic sheets during printing with larger nozzles, hence, these printed electrodes could possess higher surface roughness/porosity at their outmost surface as the graphitic sheets experience less alignment. The kinetic study of the charge storage also demonstrates the increase in the diffusion-controlled charge storage (i.e., slow kinetic charge storage mechanism) in thicker electrodes possibly due to more available diffusion pathways, which might be due to higher surface roughness/porosity at the outmost surface of these electrodes.…”