The stability of MEA in SPE water electrolysis for hydrogen production

摘要

Membrane electrode assemblies (MEAs) for water electrolysis were prepared by decal transferring an Ir black anode and a Pt black cathode on the two sides of a per-fluorosulfonate solid polymer electrolyte (SPE) Nafionll2 membrane. Performance stability of an MEA with 4 cm~2 effective electrode area was tested for 208 h in a single cell water electrolysis setup. The catalysts of both electrodes on the MEAs were characterized by means of XPS and XRD. Samples of feed water were analyzed by using conductivity meter, inductance coupling plasma optical emission spectroscopy (ICP-OES), ionic chromatog-raphy and total organic carbon (TOC) analyzer. Surface oxidation of the anodic Ir catalyst was evidenced, from the original metal Ir to 71.5% Ir_2O_3 and 28.5% IrO_2 after 208 h of electrolysis. While the metallic state of Pt on the cathode did not change during the same period of operation, the crystallite size of the Pt catalyst increased from 9.1 nm to 9.8 nm. Water analysis shows there is significant accumulation of impurities in the feed water, which can contaminate the MEA. Fortunately, the MEA restored more than 98% of its original performance after a simple treatment with 1 mol/L H_2SO_4 solution. This indicates the short period performance decline of the MEA is mainly caused by a recoverable contamination.