Surface Patterning of Porous Transport Layer Structure Facilitating Mass Transfer in PEM Water Electrolysis

Abstract

Proton Exchange Membrane Water Electrolyzer (PEMWE) suffers from mass transfer limitation under high current density, in which many efforts are contributed to the structural optimization and material design of porous transport layer (PTL), with few attempts at optimizing its wettability. To further reduce the mass transfer losses, we develop a surface patterning strategy to treat the titanium (Ti) felt based on laser processing and polytetrafluoroethylene hydrophobic treatment. Compared to commercial titanium felt, it achieves the voltage of ~2.28 V at ultrahigh operating current density (5 A/cm2), reducing mass transfer losses by approximately 85.4%. Both the visualization characterization and numerical simulation results indicate that the surface patterning titanium felt has suffcient bubbles’ detachment sites, possessing the minimum average bubble diameter of 192 μm and a robust bubbles’ dynamics. The surface patterning structure efficiently restricts the bubbles’ growth and accelerates their removal, thereby achieving an efficient separate pathways for gaseous oxygen and liquid water transport in the PTL. The insights not only shed light on the fundamentals among PTL wettability and bubble dynamics, but also provide design guidelines for porous media to enable low overpotential of mass transportation.

Keywords: PEM water electrolysis, Surface patterning titanium felt, Gas-liquid transmission, Mass transfer optimization