A. Di Blasi, S. Siracusano, V. Baglio, N. Briguglio, A. Stassi, V. Antonucci, A.S. Aricò
PEM electrolyzer, stack, IrO2, nanosized catalyst, oxygen evolution reaction, hydrogen production
Electrolysis systems based on PEMs have a number of advantages in comparison to the traditional alkaline electrolyzers, such as ecological cleanliness, considerably smaller mass–volume characteristics and, essentially, a high degree of gases purity. The main disadvantage of PEM electrolysis is the high cost, due to the use of noble metal catalysts, perflurinated membranes etc. The high anode overpotential is the limiting factor for the whole process and, together with the large reversible potential, it mainly contributes to the energy supply necessary to run the PEM electrolyzer. It is therefore important to find an optimal oxygen-evolution electro-catalyst in order to minimize the energy loss. In this work, a nanosized IrO2 anode catalyst for water electrolysis was prepared by a sulfite-complex route. The electrochemical properties of the catalyst were investigated in a single cell (5 cm2 geometrical area). To assess the properties of the IrO2-based membrane-electrode assembly (MEAs) in an electrochemical device of an appropriate size, a short stack (3 cells of 100 cm2 geometrical area) PEM electrolyzer (Fig.1a) was assembled and characterized by polarization, impedance spectroscopy and chrono-amperometric measurements. The amount of H2 produced was 80 l•h-1@ 60 A under 330 W of applied electrical power. The stack electrical efficiency at 60 A and 75 °C was 70 and 81% (Fig.1b) with respect to the low and high heating value of hydrogen, respectively.