International Journal of Hydrogen Energy, Vol.44, No.29, 14467-14480, 2019
Experimental studies of natural convective mass transfer in a water-splitting system
The present research investigates the mass transfer processes at the electrode-electrolyte interface of a water-splitting, electrochemical cell using particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF). In a water-splitting device, mass transfer mechanisms usually involve simultaneous convection, diffusion, and migration. Mass transfer rate, at the electrode/electrolyte interface, depends on various factors, including electrode orientation, current density, type of redox agents and the products. The parameters considered here are cell voltage, the orientation of electrode, and the effect of concentration gradient induced by the reactants depletion and product formation at the interface on the mass transfer rate. The present study captures the instantaneous velocity and concentration fields using PIV and PLIF techniques. Conducting the experiments over various current densities and electrode-orientations, present study observes that the reactant depletion and product formation at the anode interface induces buoyancy which in turn causes natural convection even at low current densities. By utilizing the effect of orientation and the natural convection induced by the reactants and products, on the mass transfer rate, the limiting current density can be enhanced, and the supersaturation of products can be prevented at the interface. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.