Self-Pumping Nanoporous Membranes Driven by Asymmetric Electrocatalytic Reactions

When two dissimilar metals are electrically connected in the presence of an aqueous solution, they can generate spontaneous fluid flows that result in either self-propulsion of freely suspended bimetallic particles, or fluid pumping if the metals are immobilized onto a solid surface. In the latter case, this can lead to novel phenomena such as catalytic micropumps. We present a numerical model of a membrane containing nanoscale cylindrical pores with platinum (Pt) coated onto one surface and gold (Au) on the opposite surface. In the presence of hydrogen peroxide, electrochemical charge-transfer reactions occur on each metal that result in a concentration gradient of protons, which in turn generates an electric field that drives electroosmotic flows through the pores. Electric double layer overlap is shown to be detrimental to self-pumping. For large pore radii, such as 6 microns, electric double layer overlap is no longer a concern and the velocity of self-pumping can exceed 20 microns per second. This work highlights the potential of utilizing catalytic reactions to pump liquid via membranes without external power, enhances the understanding of the physics underlying self-pumping flow, and provides guidance on the designing the next generation of self-pumping devices.