Single atom-metallic particle interaction enhances the catalytic stability for oxygen reduction reaction (ORR). However, its related mechanism has not been fully understood. Herein, the interaction between a single atom site and metallic particles and its effect on promoting catalyst stability was quantitatively described, taking the example of a single atom of Fe. Metallic particles, as electron donors, decreased the Fe valence by increasing the electron density at the FeN4 position. Subsequently, this strengthened the Fe-N bond and inhibited the electrochemical Fe dissolution, boosting the catalyst stability. Different metals (like Pt, Pd, Au, Ag, Fe, Co, and Ni), existence forms (like particle size, distance, and crystallinity), and content strengthen the Fe-N bond to different extents. A linear correlation between Fe valence, Fe-N bond strength, and electrochemical Fe dissolution amount in single atom-particle catalyst systems experimentally and theoretically supported this mechanism. Consequently, a stable particle-assisted Fe-based ORR catalyst that could operate stably up to 430 h in a direct methanol fuel cell (DMFC) was screened, ranking among the best non-precious ORR catalysts. This study helps to develop cheap yet stable catalysts for fuel cell applications.
Demetalation, caused by the electrochemical dissolution of metal atoms, poses a significant challenge to the practical application of single-atom catalytic sites (SACS) in proton exchange membrane-based energy technologies. One promising approach to inhibit SACS demetalation is the use of metallic particles to interact with SACS. However, the mechanism underlying this stabilization remains unclear. In this study, we propose and validate a unified mechanism by which metal particles can inhibit the demetalation of Fe SACS. Metal particles act as electron donors, decreasing the Fe valence by increasing the electron density at the FeN4 position, thereby strengthening the Fe-N bond, and inhibiting electrochemical Fe dissolution. Different types, forms, and contents of metal particles increase the Fe-N bond strength to varying extents. A linear correlation between Fe valence, Fe-N bond strength, and electrochemical Fe dissolution amount supports this mechanism. Our screening of a particle-assisted Fe SAC led to a 78% reduction in Fe dissolution, enabling continuous operation for up to 430 hours in a fuel cell. These findings contribute to the development of stable SACS for energy applications.
Single atom-metallic particle interaction enhances the catalytic stability for oxygen reduction reaction (ORR). However, its related mechanism has not been fully understood. Herein, the interaction between a single atom site and metallic particles and its effect on promoting catalyst stability was quantitatively described, taking the example of a single atom of Fe. Metallic particles, as electron donors, decreased the Fe valence by increasing the electron density at the FeN4 position. Subsequently, this strengthened the Fe-N bond and inhibited the electrochemical Fe dissolution, boosting the catalyst stability. Different metals (like Pt, Pd, Au, Ag, Fe, Co, and Ni), existence forms (like particle size, distance, and crystallinity), and content strengthen the Fe-N bond to different extents. A linear correlation between Fe valence, Fe-N bond strength, and electrochemical Fe dissolution amount in single atom-particle catalyst systems experimentally and theoretically supported this mechanism. Consequently, a stable particle-assisted Fe-based ORR catalyst that could operate stably up to 430 h in a direct methanol fuel cell (DMFC) was screened, ranking among the best non-precious ORR catalysts. This study helps to develop cheap yet stable catalysts for fuel cell applications.
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