Computational Optimization of Porous Structures for Electrochemical Processes

Abstract

Porous structures are naturally involved in electrochemical processes. The specific architectures of the available porous materials, as well as their physical properties, crucially affect their applications, e.g., their use in fuel cells, batteries, or electrolysers. A key point is the correlation of transport properties (mass, heat, and charges) in the spatially—and in certain cases also temporally—distributed pore structure. In this paper, we use mathematical modeling to investigate the impact of the pore structure on the distribution of wetting and non-wetting phases in porous transport layers used in water electrolysis. We present and discuss the potential of pore network models and an upscaling strategy for the simulation of the saturation of the pore space with liquid and gas, as well as the computation of the relative permeabilities and oxygen dissolution and diffusion. It is studied how a change of structure, i.e., the spatial grading of the pore size distribution and porosity, change the transport properties. Several situations are investigated, including a vertical gradient ranging from small to large pore sizes and vice versa, as well as a dual-porosity network. The simulation results indicate that the specific porous structure has a significant impact on the spatial distribution of species and their respective relative permeabilities. In more detail, it is found that the continuous increase of pore sizes from the catalyst layer side towards the water inlet interface yields the best transport properties among the investigated pore networks. This outcome could be useful for the development of grading strategies, specifically for material optimization for improved transport kinetics in water electrolyser applications and for electrochemical processes in general.

Multiphysics modeling of proton exchange membrane water electrolysis: From steady to dynamic behavior

“…This high liquid saturation can also be reflected by the large oxygen mass fraction in the anode, as shown in Figure S1A,B, since the large liquid water content results in a high reaction rate in the aCL. The similar high‐dimensional simulation can be also found in the work of Paliwal et al 42 and Vorhauer‐Huget et al 43 Figure 7B demonstrates that the porosity gradient has slight effects on the species transport in cCL and cPTL subdomains, due to the simple movement of two‐phase flow in the cathode chamber. Interestingly, compared with the production mass fraction of both specific porosity gradient cases in the cathode, the transient processes indicate that the HP to LP case provides faster final steady time and more homogeneous distribution (seen in Figure S1C,D).…”

“…This high liquid saturation can also be reflected by the large oxygen mass fraction in the anode, as shown in Figure S1A,B, since the large liquid water content results in a high reaction rate in the aCL. The similar high-dimensional simulation can be also found in the work of Paliwal et al 42 and Vorhauer-Huget et al 43 Lee et al 26 ever suggested that a PEMWE preferred the micropore PTL with the LP to HP design, based on their contrary computational results compared with us. This difference may result from the our neglecting the interfacial pore coverage at the CL/PTL interfaces.…”

Numerical Modeling and Topology Optimization for Designing the Anode Catalyst Layer in Proton Exchange Membrane Water Electrolyzers Considering Mass Transport Limitation

“…7a, since the larger pores are capable of efficiently driving two-phase substances to the reaction site. Moreover, the variation in void management can also be observed through the pore models studied by Vorhauer et al 58 and Paliwal et al 59 Such a formation of porosity distribution was not observed when the mass transport limitation was not considered. The structure of void at the low voltage optimization point (1.73 V) creates a smaller length and less number of channels than the high optimization point (2.03 V).…”

Methodology for Concurrent Multi-Parametric Physical Modeling of a Target Natural Unfractured Homogeneous Sandstone

“…To better exploit and manage these valuable resources, researchers need both numerical and physical simulation tools of sufficient sophistication. Numerical simulation tools have seen dramatical improvement with advances in computing power and software sophistication [6,7]. Advances in 2D microfluidic devices have enabled better understanding of the transport phenomenon at the microscale through addition of the visual component [8,9].…”