Preparation and characterization of G/Ni-PTFE electrode using Ni-PTFE composite plating for alkaline fuel cells

摘要

Graphite particles (80 μrn) 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 Sim~(-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 ℃. The surface of C/Ni-PTFE plates contained infinitely many gaps of 0.01-20μm; 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 x 10~3 Sm~(-3)) higher than those of the PTFE/Ni-PTFE plates. Furthermore, the total pore volume (0.145 cm~3 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.