Optimizing the Porous Transport Layer and Catalyst Layer Interfacial Contact and Operating Protocol for PEM Water Electrolyzer Cells

Abstract

Proton exchange membrane electrolyzer cells (PEMECs) are electrochemical energy conversion devices, which can provide a pathway to store electrical energy in the form of hydrogen through a water splitting process [1, 2]. Numerous studies in this research area focused on improving cell performance and durability, and lowering cost [3]. The porous transport layers (PTLs), that are key components within these devices, facilitate mass transport, thermal and electrical conduction, and are required to sustain a good interfacial contact with adjacent components [4, 5]. The interfacial contact properties between adjacent components in PEMECs have great influence on cell performance and durability [6, 7].In this study, the effects of interfacial contacts between PTLs and catalyst layers (CLs) are comprehensively investigated by adopting various operating protocols, including step scan, dynamic sweep scan, galvanostatic and potentiostatic control. We also compare wet/dry and wet/wet operating modes on cells by using PTLs with and without protective coatings. The impacts of current and voltage perturbation amplitudes for conducting EIS diagnostics are also studied. Figure 1 highlights the performance effects of adding an Ir coating onto a Ti based PTL. The data indicate that the performance is significantly improved due to the Ir coating. Identical improvement is accomplished when coating the PTL with platinum. Therefore, we assign the observed improvement to the reduction of the electrical contact resistances, and assume that the Ir coating does not significantly contribute to the electrochemical reaction as discussed by Liu et al. [8]. In addition, the current dependence of the cell resistance that is observed for operation with uncoated PTL materials disappears for cells with Ir coated PTLs. This effect is assigned to the improved heat conduction properties at the PTL/CL interface as depicted in Figure 2. Results will be discussed that focus on the optimization of performance with regards to the impact of the PTL/CL interface and operating strategy.