Proton Conductive Areas on Sulfonated Poly(Arylene Ketone) Multiblock Copolymer Electrolyte Membrane Studied by Current-Sensing Atomic Force Microscopy

Abstract

Proton conductive spots on the membrane surface of sulfonated poly(arylene ketone) multiblock copolymer were investigated by current-sensing atomic force microscopy (CS-AFM) under the hydrogen atmosphere with changing relative humidity, temperature, and bias voltage. The bright spots, where the hydrophilic clusters should be effectively connected inside the membrane, were distributed rather inhomogeneously on the surface at low temperature and humidity but became more homogeneous at higher temperature and humidity. The average diameter of the spots was approximately 10 nm at 40% RH, which increased to 13 nm at 70% RH. The total area of the proton conducting spots, as well as current at each spot, on the membrane surface increased at high humidity and temperature. In addition, the diameter of the proton-conductive spots and the ratio of proton-conductive area on the membrane surface continuously increased with increasing the bias voltage. This increase of the conducting area and the current should be related to the change of the bulk ionic conductivity.

Double-Layer Ionomer Membrane for Improving Fuel Cell Performance

“…Such catalyst particles are covered by Nafion binder and would thus be active in the CV measurements (under nearly static conditions) to account for reasonable ECSA values but would not function in the operating fuel cells (under dynamic conditions) because of insufficient proton supply from the membrane. , The Nafion interlayer was effective in improving the interfacial contact between the SPK- bl -1 membrane and the cathode catalyst layer. The effect of the interlayer was most striking at 30% RH, presumably because the proton-conductive path at the surface of the SPK- bl -1 membrane was least developed at low humidity as confirmed by electrochemical AFM analyses . The mass activity of the SPK–Nafion-cell was 43.1 A g Pt –1 at 30% RH, which was comparable to that of the NRE211-cell (46.1 A g Pt –1 ).…”

“…The effect of the interlayer was most striking at 30% RH, presumably because the proton-conductive path at the surface of the SPK-bl-1 membrane was least developed at low humidity as confirmed by electrochemical AFM analyses. 15 The mass activity of the SPK−Nafion-cell was 43.1 A g Pt −1 at 30% RH, which was comparable to that of the NRE211-cell (46.1 A g Pt −1 ).…”

Properties and Morphologies of Anion-Exchange Membranes with Different Lengths of Fluorinated Hydrophobic Chains

“…Figure shows the topographic images of QPAF­(C4)-4 (a) and QPAF­(C6)-4 (b) and the current images of QPAF­(C4)-4 (c) and QPAF­(C6)-4 (d) obtained by current-sensing atomic force microscopy (CS-AFM). − The topographic and current images were simultaneously measured. The surface roughness of the QPAF­(C4)-4 and QPAF­(C6)-4 membranes was approximately 15 nm.…”

“…CS-AFM measurements were carried out at 40 °C and 70% RH with a commercial AFM system (SPM-5500, Agilent) under ultrapure air (CO 2 less than 5 ppb). − OH – ions formed at the cathode at a silicon AFM tip (Nanoworld) coated with Pt–Ir alloy were transferred to the anode through the AEM and oxidized to oxygen at the anode . Topographic and current images were simultaneously obtained in the contact mode (contact force = 5 nN, tip voltage = −0.2 V).…”