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

Abstract

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 °C. The effective surface area of the membrane was 20 cm2 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 °C in H2/O2, and the stack produces a near-constant power output of 31.6 W in H2/air at 150 °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 °C in H2/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.