Design and experimental research of a novel droplet flow field in proton exchange membrane fuel cell

• A novel droplet flow field structure is proposed. • The droplet flow field exhibits excellent oxygen transport capacity. • The variable-diameter structure is beneficial to water management. • A uniform current density distribution is obtained in the droplet flow field. • The droplet flow field facilitates a reduction in the pressure drop. The flow field plays a vital role in the performance and cost of the proton exchange membrane fuel cell (PEMFC). However, the traditional flow field structure cannot meet the high-power density requirements of PEMFC commercialization due to poor mass transport capacity. In addition, new flow field designs have some problems, such as complicated structure, high pressure drop and high manufacturing cost, which make them unsuitable for large-scale applications. In this paper, a novel droplet flow field (DFF) structure is proposed to further improve cell performance and reduce manufacturing cost. In particular, in-situ electrochemical measurement and printed circuit board segmented fuel cell technology are used to investigate the performance of cells with different DFFs. Based on the experimental results, the mass transport mechanism of DFF and its influence on the cell performance and current density distribution are deeply analyzed. The results indicate that DFFs have excellent oxygen transport and water management capabilities, thus improving the cell performance, especially at high current density. By optimizing the droplet placement direction in DFF, we found that the structure with the gas flow direction in contact with the droplet tail (DFF(a)) has the highest cell performance. Compared with the conventional parallel flow field, the maximum power density of the DFF(a) can be increased by 23.7%. Also, the introduction of droplet structure improves the current density distribution uniformity. Furthermore, DFFs have a lower pressure drop, which reduces the pump parasitic power and increases the PEMFC system net output power. Considering the cell performance, current density distribution uniformity and pressure drop, we think that the DFFs (especially the optimized DFF(a)) are more suitable for the practical application of PEMFC.