Stack performance of phosphotungstic acid functionalized mesoporous silica (HPW-meso-silica) nanocomposite high temperature proton exchange membrane fuel cells

In this paper, a series of short stacks with 2-cell, 6-cell and 10-cell employing phosphotungstic acid functionalized mesoporous silica (HPW-meso-silica) nanocomposite proton exchange membranes (PEMs) have been successfully fabricated, assembled and tested from room temperature to 200 degrees C. The effective surface area of the membrane was 20 cm(2) and fabricated by a modified hot-pressing method. With the 2-cell stack, the open circuit voltage was 1.94 V and it was 5.01 V for the 6-cell stack, indicating a low gas permeability of the HPW-meso-silica membranes. With the 10-cell stack, a maximum power density of 74.4 W (equivalent to 372.1 mW cm(-2)) occurs at 150 degrees C in H-2/O-2, and the stack produces a near-constant power output of 31.6 W in H-2/air at 150 degrees C without external humidification for 50 h. The short stack also displays good performance and stability during startup and shutdown cycling testing for 8 days at 150 degrees C in H-2/air. Although the stack test period may be too short to extract definitive conclusions, the results are very promising, demonstrating the feasibility of the new inorganic HPW-meso-silica nanocomposites as PEMs for fuel cell stacks operating at elevated temperatures in the absence of external humidification. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.