Effects of Porous Material Properties and Operating Conditions on PEM Electrolysis Performance and the Observation of Mass and Heat Transport

Abstract

Polymer electrolyte membrane water electrolysis (PEMWE) is a promising technology for the integration and utilization of renewable energy and hydrogen as an energy carrier. Advancements in catalysis have made the commercial viability outlook very encouraging. Nonetheless, more work is necessary to advance the technology from niche markets towards broad market penetration. Through this study, we increase understanding of transport and interfacial phenomena, which can be used to design more efficient electrolyzers and improve cell performance. Preventing excessive oxygen accumulation in the catalyst layer (CL) by adjusting the geometry and properties of flow channels, the porous transport layer (PTL), and the CL itself may result in increased catalyst utilization, efficiency, and performance. Controlling feed water to allow a significant increase in CL temperature may also improve efficiency. In order to optimize performance without operating under conditions that may affect cell durability, PEMWE scale-up relies on robust models that accurately predict current and temperature distributions. Such models, particularly 3-D flow models, provide the opportunity to improve electrolysis efficiency through process engineering. Electrochemical models have been commonly used to fit known relationships to the measured performance of PEMWE devices. Computational modeling is a lean approach to enhancing technology without the cost and duration of experimentation, albeit via the quantitative understanding of prior empirical observations. This work investigated the effects of experimental parameters on transport, highlighting the need to accurately model temperature elevation and gas inhabitation in the CL. This was done in order to develop and validate a 3-D PEMWE model that predicts current distribution and overall cell efficiency using computational fluid dynamics (CFD) simulations. The following experiments examined a PEMWE device under a wide range of conditions in order to uncover information about multiscale phenomena that may improve the model. The experimental parameter space was designed minding the importance of the through-plane pressure drop in the PTL and the temperature rise in the CL. It included variation of current density, inlet water flow rate, temperature, and properties of cell components. Polarization curves and complimentary Nyquist plots from electrochemical impedance spectroscopy (EIS) were used in addition to inlet/outlet temperatures and cell pressure drop to observe mass and heat transport. A summary of the findings from the main validation experiments and their interpretations will be discussed.