Multiple in-situ measurement of water transport in the bipolar plate of proton exchange membrane fuel cell

•Water management is a key factor in improving the performance and durability of PEMFC.•The reliability test of the micro RH/T sensors was conducted.•A unit cell PEMFC with built-in micro RH/T sensors was fabricated.•Temperature, water concentration and water transport were investigated through the in-plane area of MEA. Water concentration inside proton exchange membrane fuel cells (PEMFCs) is a key factor affecting performance and durability. Therefore, many studies have been conducted to maintain an appropriate moisture balance inside the stack. The most recent study was a study that confirmed moisture distribution using five sensors inside the anode and cathode. However, in this study, it is difficult to determine the exact moisture distribution inside the stack due to insufficient sensors. In this study, a unit cell PEMFC including micro relative humidity and temperature (RH/T) sensors with an active area of 100cm2 was fabricated to characterize the water concentration. Before installing the micro sensors into the bipolar plates, a reliability test is conducted, and the result shows that the sensor is reliable at 60 °C and 70 °C. After that, for the in-situ temperature and relative humidity measurement, the 50 sensors are installed along the anode and cathode gas channels evenly in the active area. This study investigates the distribution of water transport behavior, temperature, and water concentration at 0.6 V, 0.5 V and 0.4 V of electric load. Dew point is introduced to analyze water concentration, and net water mole flux is calculated to evaluate water transport behavior. The results show that as the load applied to the PEMFC increases, higher temperature band expands from downstream to upstream of the gas flow. In addition, at 0.4 V, observing the highest temperature band between 61 °C to 62 °C, it is concluded that the flow field of the reaction zone is more activated along the downstream. Meanwhile, the anode becomes more dehydrated with higher load and the cathode more hydrated. At 0.4 V, the maximum dew point on the cathode is 37.5 °C, and the minimum dew point on the anode is 30 °C. In conclusion, even though water transports from the cathode to the anode, due to dry inlet gas, 20% of relative humidity, and high flow rate, hydrogen by 2.8lpm and air by 6.65lpm, the anode doesn't become hydrated.