(675h) Advanced Mass Transport Properties of 3D-Printed Porous Periodic Lattice Graphene Flow-through Electrodes

Since heterogeneous electrochemical reactions under conditions relevant to commercial applications depend on mass transport, liquid type reactors gain efficiency from forcing solutions through 3D porous flow-through electrodes with high internal surface area and enhanced mixing properties. We consider electrochemical reactor design based on maximizing mass transport performance and explore electrodes with periodic lattices enabled by additive manufacturing fabrication tools. Controllable periodic pore structure electrodes solve the problem of uneven velocity distribution (channeling) known to decrease mass transport rates in disordered porous foams and felts and enable engineering of flow patterns for improving mass transport. In this report, by means of numerical simulation and experiment, we study flow rate dependent mass transport of periodic porous lattice electrodes prepared by direct ink write method as simple cubic and face centered cubic structures with 0.8 mm lattice parameter using 0.4 mm nozzle. Volumetric mass transport coefficients were assessed from limiting currents measured for simple one electron transfer reaction in ferrocyanide solutions as a function of flow rates. Results show that while staying at laminar regime (Re < 10), the power-law exponent of mass transfer coefficient as a function of flow velocity increases from about 0.4 to 0.6 after threshold velocity is reached. Typically, sharp increases in the power-law exponent are observed due to changing from laminar to turbulent regimes at much higher Re numbers (Re > 1000). Numerical simulations reveal that scaling factor increase at much lower Re numbers in this work was possible due to controlled geometry of printed electrode allowing generation of secondary flow patterns promoting enhanced local mass transport as flow switches from viscous to inertial. Electrodes that yield high mass transport coefficients at low flow velocity are advantageous due to the pumping power inefficiencies present at high velocities. Further improvements in the mass transport properties can be achieved by 3D-printing lattices with modified design parameters (e.g. pore size, filament diameter, lattice structure, etc.). The results are discussed in the context of theory and previous literature.