Experimental study on a unitized regenerative fuel cell operated in constant electrode mode: Effect of cell design and operating conditions

Constant electrode (CE) operation of a unitized regenerative fuel cell (URFC) facilitates the optimization of each electrode. In this work, bipolar plates (BPPs) with different flow fields (FFs) are assessed, and a graphite BPP is compared with a titanium BPP in the cathode. Platinum coated titanium felt and carbon cloth and paper gas diffusion layers (GDLs) are tested in the cathode. The carbon BPP and GDLs operated with higher ohmic resistance than the titanium alternatives. However, the titanium GDL caused flooding in FC mode. Carbon GDLs can be applied in the cathode, where carbon paper operated with higher performance than carbon cloth. Titanium GDL is still required in the anode to resist the corrosive environment. A double-serpentine FF in the cathode and a parallel design in the anode were applied. Optimization of the URFC operating conditions under FC mode provided the best results at 80 degrees C, 2 barabs, with saturated air and dry hydrogen and stoichiometry ratios of 2 and 8. This resulted in a round-trip efficiency of 56% at 0.1 A cm-2, 48% at 0.3 A cm-2 and 22% at 1 A cm-2. In comparison, 56%, 52% and 37% were obtained with a discrete regenerative fuel cell (DRFC).

Automated summary

This study compares the performance of different bipolar plates and gas diffusion layers in a unitized regenerative fuel cell. The results show that carbon materials perform better in the cathode, while titanium materials are still required in the anode. Additionally, optimizing the operating conditions of the URFC can improve its efficiency.