Oxygen reduction reaction electrocatalysts based on FeSn0.5 species embedded in hierarchical CN-graphene based supports

TL;DR

This study develops platinum-free electrocatalysts for the oxygen reduction reaction using FeSn0.5 species embedded in hierarchical CN-graphene supports, revealing how physicochemical properties influence performance and mechanism.

Contribution

It introduces a novel hierarchical CN-graphene support with FeSn0.5 active sites and analyzes the effects of activation and pH on ORR performance.

Findings

Activation improves ORR kinetics.

Physicochemical properties correlate with electrochemical performance.

Insights into active site features and ORR mechanism.

Abstract

This work reports the synthesis, the physicochemical characterization and the electrochemical studies of new electrocatalysts (ECs) for the oxygen reduction reaction (ORR) that: (i) are based on a hierarchical graphene-based support; and (ii) do not comprise platinum. The active sites of the ECs consist of Fe and Sn species stabilized in 'coordination nests' of a carbon nitride (CN) matrix. The latter exhibits a rough, microporous morphology and acts as a 'shell' covering a graphene 'core'. This paper: (i) discusses the role played by Fe as the 'active metal' in this family of ECs; and (ii) examines in detail how the physicochemical properties and, correspondingly, the electrochemical performance are affected by a suitable activation procedure A meant to boost the ORR kinetics. The results lead to an improved fundamental understanding on the features of the active sites, including the impact of both A and the pH of the environment in their performance and ORR mechanism. These insights clarify the most desirable features to be included in high-performing ECs belonging to this family, paving the way to the synthesis of next-generation, efficient ECs for the ORR that do not comprise platinum.