(Co, Ni)Sn0.5 nanoparticles supported on hierarchical CN-graphene-based electrocatalysts for the oxygen reduction reaction

TL;DR

This study develops hierarchical graphene-based electrocatalysts with Co and Ni Sn0.5 nanoparticles for the oxygen reduction reaction, demonstrating improved performance and stability in a 'Pt-free' system through chemical and morphological optimization.

Contribution

Introduces a new class of hierarchical CN-graphene electrocatalysts with Co and Ni Sn0.5 nanoparticles, enhancing ORR performance without platinum.

Findings

Hierarchical 'core-shell' morphology improves ORR activity.

Activation process enhances electrocatalyst performance.

CN matrix stabilizes nanoparticles and boosts durability.

Abstract

The synthesis of new 'Pt-free' electrocatalysts (ECs) for the oxygen reduction reaction (ORR) is reported. The ECs are characterized by a hierarchical 'core-shell' morphology; the 'core' is made of graphene, that is covered by a cratered, microporous carbon nitride (CN) 'shell'. The latter supports nanoparticles of M1 and Sn metals (M1 = Co; Ni) in 'coordination nests'. These latter are holes in the CN matrix, whose walls consist of N- and C-ligands. Two groups of ECs are studied: (i) 'pristine' ECs; and (ii) 'activated' ECs, that are obtained from the 'pristine' ECs by means of a suitable activation process (A) aimed at improving the performance in the ORR. Here is clarified the interplay existent between: (i) the chemical composition, morphology, structure and A; and (ii) the ORR performance and mechanism as a function of the pH of the environment. The resulting insights improve the fundamental understanding of this family of ECs and open the door to the devising of new preparations of 'Pt-free' ECs for the ORR, which: (i) are stabilized by a CN matrix and; (ii) exhibit an improved performance.