Clusters Induced Electron Redistribution to Tune Oxygen Reduction Activity of Transition Metal Single‐Atom for Metal–Air Batteries

Abstract

Oxygen reduction reaction (ORR) activity can be effectively tuned by modulating the electron configuration and optimizing the chemical bonds. Herein, a general strategy to optimize the activity of metal single‐atoms is achieved by the decoration of metal clusters via a coating–pyrolysis–etching route. In this unique structure, the metal clusters are able to induce electron redistribution and modulate M−N species bond lengths. As a result, M‐ACSA@NC exhibits superior ORR activity compared with the nanoparticle‐decorated counterparts. The performance enhancement is attributed to the optimized intermediates desorption benefiting from the unique electronic configuration. Theoretical analysis reinforces the significant roles of metal clusters by correlating the ORR activity with cluster‐induced charge transfer. As a proof‐of‐concept, various metal–air batteries assembled with Fe‐ACSA@NC deliver remarkable power densities and capacities. This strategy is an effective and universal technique for electron modulation of M−N−C, which shows great potential in application of energy storage devices.

Electronic Control of Traditional Iron–Carbon Electrodes to Regulate the Oxygen Reduction Route to Scale Up Water Purification

“…Downsizing active species to a single-atom scale not only promotes the maximum atom utilization efficiency but also results in unique electronic properties for tuning binding strength with reaction intermediates. − Generally, the geometric and electronic structures of atomic metal sites can be engineered by their local coordination environment with other elements (O, B, S, P, etc. ). , However, it is difficult to modify the electronic structures merely through the introduction of heteroatoms due to the reason of the poor control of uniformity and dispersion. , Notably, controlling the long-range activation through interfacial interaction created by electron-donating/-withdrawing species can be a promising approach for tuning the electronic structure of single metal centers. − Sub-nanometric metal clusters exhibited excellent catalytic performance because of coordinatively unsaturated surface atoms, − resulting in electron delocalization and tunable electronic properties. , …”

Hierarchal Porous Graphene-Structured Electrocatalysts with Fe–N5 Active Sites Modified with Fe Clusters for Enhanced Performance Toward Oxygen Reduction Reaction

“…28 enhanced ORR activity. 29 As a result, it is feasible to enhance the catalytic activity of the SA-Fe−N−C catalyst with numerous N−Fe−N 4 moieties near atomic Fe clusters. Moreover, in most of the previous studies of SA-Fe−N−C that utilized ZIF as the precursors, it has been revealed that the catalysts will inherit the microporous structures of the precursors.…”

“…Also, the adsorption of oxygen-containing intermediates on the central Fe atoms with σ-type bonding would be greatly modulated during the ORR process. − Thus, the generated *OH intermediates on the central metal atom can pull the central Fe back into the N 4 plane and convert the spin state of Fe centers from high back to low, eventually reducing the energy barrier for the ORR process. ,, In addition, it is reported that the electronic structure of single-atom sites can be also modified by the existence of the atomic clusters nearing these single-atom sites . For example, Huang et al reported that a Fe cluster-decorated SA-Fe–N–C catalyst with a unique electronic configuration, which shows that the redistribution of electrons on Fe–N 4 centers induced by atomic clusters exhibits an enhanced ORR activity . As a result, it is feasible to enhance the catalytic activity of the SA-Fe–N–C catalyst with numerous N–Fe–N 4 moieties near atomic Fe clusters.…”

Metal‐Organic‐Framework‐derived Co Nanoparticles Embedded in P, N‐Dual‐doped Porous Carbon/rGO Catalyst for Water Splitting and Oxygen Reduction

“…The worldwide energy crisis prompted extensive and methodical study into energy conversion and storage. [1][2][3][4] Electrocatalytic oxygen reduction reactions (ORR), [5,6] hydrogen evolution reactions (HER) [7] and oxygen evolution reactions (OER) [8] play an important role in various energy technologies, including fuel cells [9][10][11][12] and water splitting. [13][14][15] The development of efficient electrocatalysts for energy conversion and storage is particularly critical.…”