Preparation and characterization of C/Ni–PTFE electrode using Ni–PTFE composite plating for alkaline fuel cells

Graphite particles (80 μm) and PTFE particles (40 μm) were coated with Ni (18–50 wt.%) and PTFE fine particles (0.3 μm; 8 wt.%) via electroless Ni–PTFE composite plating. The conductivity of Ni–PTFE plated graphite (C/Ni–PTFE) and PTFE (PTFE/Ni–PTFE) particles increased with the Ni content. At 35 wt.% Ni content, the conductivity (300 Sm−1) of C/Ni–PTFE particles was about 2 times higher than that of PTFE/Ni–PTFE particles. The particles were pressed into plates under a pressure of 10–500 kg cm−2 and the plates were then subjected to heat treatment at 350 °C. The surface of C/Ni–PTFE plates contained infinitely many gaps of 0.01–20 μm; these gaps are useful as a pathway for reacting gases. The conductivities in a direction perpendicular and parallel to the C/Ni–PTFE plates were respectively about 3.5 times (510 Sm−1) and 16 times (48 × 103 Sm−1) higher than those of the PTFE/Ni–PTFE plates. Furthermore, the total pore volume (0.145 cm3 g−1) of C/Ni–PTFE plates was higher than that of PTFE/Ni–PTFE plates, which improved the gas permeability of the former. The current density (84 mA cm−2 at 0.3 V) of C/Ni–PTFE electrode was about 2 times higher than that of PTFE/Ni–PTFE electrode. This increase in the current density might be attributed to the improvement in the total conductivity and gas permeability of C/Ni–PTFE electrode.