Unusual influence of binder composition and phosphoric acid leaching on oxygen mass transport in catalyst layers of high-temperature proton exchange membrane fuel cells

Abstract

Oxygen mass transport in the cathode catalyst layer (CCL) of high-temperature proton exchange membrane fuel cells (HT-PEMFCs) plays an important role in promoting the fuel cell performance. The objective of this study is the development of suitable tools and analytical methods for quantitatively characterizing O2 mass transport coefficients in a binder used in HT-PEMFCs from a microscopic and local perspective. A microelectrode electrochemical system with high sensitivity and stability is built in-house. High-resolution cyclic voltammetry, potential-step chronoamperometry and sampled chronoamperometry at the nA scale are successfully performed in a shielding box to determine the O2 mass transport coefficients in a poly (ethersulfone)-poly (vinyl pyrrolidone) (PES-PVP) blend binder with different PVP contents. In addition, we investigate the effect of phosphoric acid (PA) leaching on O2 mass transport in the binder, which is generally used to explain the decline in membrane conductivity. Linear regression analysis reveals that the permeability of O2 in binder can be affected significantly by the PVP content and the PA doping level of the binder in CCL.