Alleviating anode flooding by mesoporous carbon supports for alkaline polymer electrolyte fuel cells

Abstract

Water management is one of the critical issues affecting the performance and stability of alkaline polymer electrolyte fuel cells (APEFCs). This study focuses on the effect of carbon supports on the water management of APEFCs. A series of carbon-supported Ru catalysts (Ru/MCP-x) were prepared using mesoporous carbon powder (MCP-x) with three-dimensional through-nanopore structures as supports and compared with Ru/XC72. The results show that although the catalysts’ hydrogen oxidation reaction (HOR) catalytic activities are similar in KOH solutions, the APEFCs performance can be severely different. APEFCs assembled with Ru/MCP-x and Ru/XC72 (noted as Ru/MCP-x cell and Ru/XC72 cell) have little performance difference at high inlet H2 flow (1000 mL/min), but have a noticeable difference at low inlet H2 flow (200 mL/min). By combining the electrochemical AC impedance and distribution of relaxation time (DRT) method, we quantitatively identify that severe gas transfer resistance occurred in the anode catalyst layer of the Ru/XC72 cell under low inlet H2 flow, which is more in line with the actual APEFCs operating conditions, led to considerable degradation of the Ru/XC72 cell performance. The high gas transfer resistance is later ascribed to the anode flooding by combining the voltammetry curves and DRT plots. In contrast, for Ru/MCP-x cells, increasing the carbon supports’ mesopore diameter dramatically reduced the gas transfer resistance and mitigated the anode flooding. This study shows a quantitative comparison of the impacts of different carbon supports on APEFCs performance and gas transfer resistance, indicating that mesoporous carbon materials have the potential to be supports for APEFCs anode catalysts to alleviate the anode flooding.