Bimetallic alloys encapsulated in fullerenes as efficient oxygen reduction or oxygen evolution reaction catalysts: A density functional theory study

Revealing the structure-activity relationship of catalysts is conducive to design high-activity catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this paper, the ORR and OER catalytic activity of bimetallic alloys encapsulated in fullerenes M1xM24−x@Cn (M1xM24−x represents FexCo4−x, FexNi4−x, CoxNi4−x; x = 1, 2, 3; n = 40, 50, 60) are investigated by density functional theory methods. The calculated encapsulation energy (Eenc) indicates that except for the value on Fe1Ni3@C60, all the Eenc values are positive on the studied M1xM24−x@Cn, suggesting that additional externally supplied energy will be needed to encapsulate bimetallic alloys in fullerenes. As the size of the Cn cage decreases, the charge transfer between the alloy core and the carbon shell becomes greater, resulting in a roughly increase in the binding strength of the reaction intermediates on M1xM24−x@Cn. Compared with C40, C50 and C60 fullerenes are recognized as the more suitable shell for encapsulating bimetallic alloys toward ORR and OER. Based on the current study, Co1Ni3@C50 is screened out with the best ORR activity (ηORR = 0.35 V) and Co2Ni2@C60 shows the most excellent OER activity (ηOER = 0.36 V) among all the M1xM24−x@Cn.