Recent progress on mechanisms, principles, and strategies for high‐activity and high‐stability non‐PGM fuel cell catalyst design

Abstract

The commercialization of a polymer membrane H2–O2 fuel cell and its widespread use call for the development of cost‐effective oxygen reduction reaction (ORR) nonplatinum group metal (NPGM) catalysts. Nevertheless, to meet the requests for the real‐world fuel cell application and replacing platinum catalysts, it still needs to address some challenges for NPGM catalysts regarding the sluggish ORR kinetics in the cathode and their poor durability in acidic environment. In response to these issues, numerous efforts have been made to study NPGM catalysts both theoretically and experimentally, developed these into the atomically dispersed coordinated metal–nitrogen–carbon (M–N–C) form over the past decades. In this review, we present a comprehensive summary of recent advancements on NPGM catalysts with high activity and durability. Catalyst design strategies in terms of optimizing active‐site density and enhancing catalyst stability against demetalization and carbon corrosion are highlighted. It is also emphasized the importance of understanding the mechanisms and principles behind those strategies through a combination of theoretical modeling and experimental work. Especially, further understanding the mechanisms related to the active‐site structure and the formation process of the single‐atom active site under pyrolysis conditions is critical for active‐site engineering. Optimizing the active‐site distance is the basic principle for improving catalyst activity through increasing the catalyst active‐site density. Theoretical studies for the catalyst deactivation mechanism and modeling stable active‐site structures provide both mechanisms and principles to improve the NPGM catalyst durability. Finally, currently remained challenges and perspectives in the future on designing high‐performance atomically dispersed NPGM catalysts toward fuel cell application are discussed.

Metal–organic framework-derived single-atom catalysts for electrocatalytic energy conversion applications

“…202–205 These emerging energy conversion and storage technologies stand to benefit from the distinctive attributes of SACs, encompassing their exceptional catalytic activity, selectivity, and stability. Within PEMFCs or DFAFCs, 206–210 SACs immobilized on MOFs demonstrate efficacy as catalysts for pivotal reactions such as the ORR, hydrogen oxidation reaction (HOR), and formic acid oxidation reaction (FAOR), pivotal for fuel cell performance. Likewise, in ZABs, MOF-supported SACs contribute to augmenting the efficiency and robustness of catalysts involved in the OER and ORR, thereby enhancing battery performance and longevity.…”

p-d Orbital Hybridization Induced by Asymmetrical FeSn Dual Atom Sites Promotes the Oxygen Reduction Reaction

“…The symmetric Fe–N 4 species with immoderate adsorption energies of the ORR intermediates (*OOH, *O, and *OH) feature limited ORR activity. − Altering the nitrogen coordination numbers of Fe center exhibited an substantial effect on ORR performance. − Besides, introducing diverse nonmetallic atoms (B, O, P, S, Se, etc.) coordinated at the first and second coordination shell of active metal sites could effectively trigger local charge redistribution and adjust the d-band energy level of metal center, on account of their distinctive atomic electronegativity and orbital interreacting. − Interestingly, the new emerging dual-metal atom catalysts have demonstrated a powerful synergetic effect to diminish the reaction barrier and hasten the catalytic kinetics, deriving from the orbital coupling between adjacent diatomic metal sites. − It is reported that the homo- and heteronuclear dual atom sites (such as Fe–Fe, Co–Co, Ni–Ni, Cu–Cu, Fe–Pt, Ru–Ni, Zn–Co, Ni–Cu, etc.)…”