Hierarchically Designed Co4Fe3@N-Doped Graphitic Carbon as an Electrocatalyst for Oxygen Evolution in Anion-Exchange-Membrane Water Electrolysis

• Published in: Energy & fuels 2024-03, Vol.38 (5), p.4451-4463
• Main Authors: Park, Seohyun, Jun, Jong Han, Park, Minjeong, Jeong, Jaehoon, Jo, Jeong-Hyang, Jeon, Sohee, Yang, Juchan, Choi, Sung Mook, Jo, Wook, Lee, Ji-Hoon
• Format: Article
• Language: English
• Subjects: Catalysis and Kinetics
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/acs.energyfuels.3c04077

Anion-exchange-membrane water electrolyzers (AEMWEs) have gained considerable attention owing to their low cost and high energy efficiency, combining the advantages of alkaline water electrolyzers (AWEs) and proton-exchange membrane water electrolyzers (PEMWEs). Despite these merits, AEMWEs face challenges associated with the insufficient electrochemical activity of transition-metal-based electrocatalysts and their inferior long-term durability, particularly in electrodes for the oxygen evolution reaction (OER). To address these issues, hierarchically structured OER electrocatalysts comprising a Co4Fe3 core and N-doped graphitic carbon shell were synthesized in this study by pyrolyzing Co/Fe–Prussian blue analogues (PBAs)-based templates. The resulting electrocatalyst demonstrated exceptional OER activity and durability, attributed to the synergy among the abundant Co3+ species, the high electrochemically active surface area, a highly conductive bimetallic alloy core, and the oxygen-enriched functional groups and pyridinic N in the N-doped carbon shell. The Co4Fe3@N-doped graphitic carbon electrocatalyst exhibited a significantly lower overpotential (245 mV at 10 mA cm–2) and enhanced mass transport kinetics (Tafel slope of 62.9 mV dec–1) compared to those of a commercialized precious metal–based IrO2 catalyst (328 mV at 10 mA cm–2 and 95.3 mV dec–1, respectively). In the AEMWE full cells, the electrolyzer based on Co4Fe3@N-doped graphitic carbon delivered a 139% higher energy efficiency and a 70 times lower performance degradation rate compared with those of the IrO2-based counterpart. The proposed PBA-based electrocatalyst can be readily synthesized using a simple synthesis process and nonprecious-metal-based materials, presenting a promising pathway for the cost-effective commercialization of AEMWEs.