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 M1(x)M(24-x)@C-n (M1(x)M(24-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 M1(x)M(24-)x@C-n, suggesting that additional externally supplied energy will be needed to encapsulate bimetallic alloys in fullerenes. As the size of the C-n 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 M1(x)M(24-x)@C-n. Compared with C-40, C-50 and C-60 fullerenes are recognized as the more suitable shell for encapsulating bimetallic alloys toward ORR and OER. Based on the current study, Co1Ni3@C-50 is screened out with the best ORR activity (eta(ORR) = 0.35 V) and Co2Ni2@C-60 shows the most excellent OER activity (eta(OER) = 0.36 V) among all the M1(x)M(24-x)@C-n. (C) 2021 Elsevier B.V. All rights reserved.