Direct Propane Fuel Cell Anode with Interdigitated Flow Fields: Two-Dimensional Model

Abstract

The first two-dimensional model of a direct propane fuel cell (DPFC) anode was developed and used to investigate materials and operating conditions that resulted in improved DPFC anode performance. The software used, FreeFEM++, is open source and is based on the finite element method. The anode catalyst layer (ACL) was composed of three phases. One solid phase was the platinum catalyst supported on porous carbon (an electron conductor). The second solid phase consisted of solid zirconium phosphate (a proton conductor at 150 °C). The gas phase was located within the pores of the carbon and between the solid particles. Operation at 150 °C allowed the propane gas phase concentration to be in direct contact with the catalyst at the entrance to the ACL. This was an important advantage compared to previous DPFC operations at conditions where aqueous liquids are present (PEMFC at temperatures less than 100 °C and direct propane PAFC). When aqueous liquids surround the catalyst, the propane concentration in contact with the catalyst at the ACL entrance is much smaller because the solubility of propane in aqueous liquids is small. The one-third improvement in the anode overpotential was attributed to this difference. By using interdigitated flow fields with the propane feed in one set of channels and the carbon dioxide product in another set of channels, there was no mixing of the two so that the maximum propane concentration was always present at the entrance to the ACL. The residence time could be chosen, by adjusting the distance between the feed and the product channels (length of land plus channel), to obtain large values of conversion and large values of fuel utilization. It was shown that the larger pressure drops often associated with interdigitated flow fields compared to conventional serpentine flow fields were diminished by increasing the thickness of the catalyst layer. In addition, the thicker catalyst layer permitted the Pt catalyst to be spread over a greater thickness of carbon catalyst support, thereby ensuring better catalyst dispersion and improved catalyst performance.

n-Hexadecane Fuel for a Phosphoric Acid Direct Hydrocarbon Fuel Cell

“…Larger molecules were studied by Ding et al [15] (octane), Kishimoto et al [16] (n-dodecane), and Zhou et al [17] (jet fuel). Our own work has focused on modeling the fuel cell reactor [18][19][20], modeling the fuel cell catalyst [21][22][23], experimental development of an electrolyte that is appropriate for temperatures above the boiling point of water [24][25][26], and experimental fuel cell studies [27,28].…”

Charge Carrier Transfer: A Neglected Process in Chemical Engineering

“…where ν ph is the phonon frequency (∼10 13 Hz), R f the rate of falloff of the wave function at the state, R the distance covered in one hop, and ∆E hop the activation energy of the hopping transport. The factor µ 0hop is 10 2 s10 3 times lower than the corresponding factor for the band transport (recall eq 29).…”

“…It is no wonder that in an age when chemical engineering is entering the fields of electrochemistry, electrostatics, and even electronics, we cannot imagine describing the processes that occur without taking into consideration just the charge carrier transfer. The growing interest in this field concerns, for example, such serious chemical engineering problems as the behavior of charged particles and droplets, − processes in electrochemical devices (e.g., fuel cells), − electronic properties of porous media, , catalytic and photocatalytic systems, − and electronic materials, − as well as the modeling and application of various plasma processes. − On the other hand, the developing molecular engineering requires a completely new look at the processes. Of course, momentum transfer, heat transfer, and mass transfer are still the governing laws here, but now their description needs a quantum approach to the problem.…”

Proton conductivity and morphology of new composite membranes based on zirconium phosphates, phosphotungstic acid, and silicic acid for direct hydrocarbon fuel cells applications

“…A two dimensional CFD model for a high temperature, direct propane fuel cell anode was developed by Khakdaman et al [2]. The results showed an improvement of the anodic performance at high temperatures.…”