Experimental study on performance evaluation of PEM fuel cell by coating bipolar plate with materials having different contact angle

Abstract

Bipolar plates that have generally been made of graphite or composite materials are a fuel cell component that must be mechanically durable, easy to process, corrosion resistant, electrically and thermal conductive in contact with a gas diffusion layer, which is a porous material. In this study, instead of developing new materials with above features, water management has been improved by coating the bipolar plates and performance review has been carried out experimentally. The flow channels of the bipolar plates were coated with PTFE and SiO2. Physical vapor deposition (PVD) was used as the coating method. After the coating process, 120.2 degrees contact angle with PTFE and 35 degrees contact angle with SiO2 was approximately obtained in the flow channels. Single cell and 3-cell stack tests were performed with bipolar plates coated with these materials and uncoated polymer composite bipolar plates for given variable O-2 and H-2 flow rate and cell temperature at constant humidification conditions. 3-cell stack were tested after assembly. In PEM fuel cell stack tests, the highest current and power density values were also obtained in the hydrophobic PTFE coated plates. But in hydrophilic fuel cell stack, no voltage and current values could be measured due to the sudden decreases due to excessive flooding of the flow channels. A decrease in power density by 12.53% was observed when the single cell having hydrophobic flow channels with coated PTFE compared to 3-cell stack at the same operating conditions.