Tailoring catalyst layer interface with titanium mesh porous transport layers

Abstract Tailoring the catalyst layer interface is paramount for high performance electrochemical energy conversion, from fuel cells to carbon dioxide electrolyzers. Here, we tailored the catalyst layer (CL) interfacial contact in a polymer electrolyte membrane (PEM) water electrolyzer with bilayer titanium mesh porous transport layers (PTLs). In contrast to typical commercial PTL materials, ohmic losses dominated the overpotentials of a PEM electrolyzer with bilayer mesh PTLs, contributing up to 73% of the overall overpotential (at a current density of 1 A/cm2). Tailoring the mesh opening size (from 1.16 mm to 0.20 mm) led to a 56% reduction in ohmic losses due to the enhanced contact between the mesh PTL and the CL. Non-negligible mass transport losses were attributed to gas pooling at the PTL/CL interface when the pore width exceeded the pore height. However, when the pore height exceeded the pore width, significantly higher mass transport losses were observed, which we attributed to complete gas filling of the pores. Additionally, we found that bilayer mesh PTLs with pore size gradients are susceptible to delamination at the CL/PTL interface due to the misalignment of mesh layers.