  Recent studies have utilized AC fields and electrochemical reactions in
multicomponent electrolyte solutions to control colloidal assembly. However,
theoretical investigations have thus far been limited to binary electrolytes
and have overlooked the impact of electrochemical reactions. In this study, we
address these limitations by analyzing a system with multicomponent
electrolytes, while also relaxing the assumption of ideally blocking electrodes
to capture the effect of surface electrochemical reactions. Through a regular
perturbation analysis in the low-applied-potential regime, we solve the
Poisson-Nernst-Planck equations and obtain effective equations for electrical
potential and ion concentrations. By employing a combination of numerical and
analytical calculations, our analysis reveals a significant finding:
electrochemical reactions alone can generate asymmetric rectified electric
fields (AREFs), i.e., time-averaged, long-range electric fields, even when the
diffusivities of the ionic species are equal. This finding expands our
understanding beyond the conventional notion that AREFs arise solely from
diffusivity contrast. Furthermore, we demonstrate that AREFs induced by
electrochemical reactions can be stronger than those resulting from asymmetric
diffusivities. Additionally, we report the emergence of asymmetric rectified
concentration fields (ARCFs), i.e., time-averaged long-range concentration
fields, which supports the electrodiffusiophoresis mechanism of colloidal
assembly observed in experiments. We also derive analytical expressions for
AREFs and ARCFs, emphasizing the role of imbalances in ionic strength and
charge densities, respectively, as the driving forces behind their formation.
The results presented in this article advance the field of colloidal assembly
and also have implications for improved understanding of electrolyte transport
in electrochemical devices.
