Pore Structure-Dependent Mass Transport in Flow-through Electrodes for Water Remediation

Hierarchical three-dimensional architectures of granphene-based materials with tailored microstructure and functionality exhibit unique mass transport behaviors and tunable active sites for various applications. The micro-/nanochannels in the porous structure can act as micro-/nano- reactors, which optimize the transport and conversion of contaminants. However, the size-effects of the micro-/nanochannels, which are directly related to its performance in electrochemical processes, have not been explored. Here, using lamellar-structured graphene films as electrodes, we demonstrate that the interlayer spacing (range from similar to 84 nm to similar to 2.44 mu m) between graphene nanosheets governs the mass transport and electron transfer in electrochemical processes; subsequently influence the water decontamination performances. The microchannel (interlayer spacing = similar to 2.44 mu m) can provide higher active surface areas, but slow reaction kinetics. Densely packed graphene nanosheets (interlayer spacing = similar to 280 nm), which possessed better electron conductivity and could provide higher surface-area-to-volume ratio in narrow nanochannels (7.14 mu m(-1)), achieved the highest reaction kinetics. However, the ion-accessible surface area was decreased in highly dense films (interlayer spacing = similar to 84 nm) due to serious interlayer stacking of graphene nanosheets, thereby leading poor reaction kinetics. These results demonstrate the size-effect of nanochannels in porous materials and highlight the importance of controlling mass transport and electron transfer for optimal electrochemical performance, enabling a deep understanding of the benefits and utilization of these hierarchical three-dimensional architectures in water purification.