Recent Advances in Atomic Metal Doping of Carbon‐based Nanomaterials for Energy Conversion

Abstract

Nanostructured metal-contained catalysts are one of the most widely used types of catalysts applied to facilitate some of sluggish electrochemical reactions. However, the high activity of these catalysts cannot be sustained over a variety of pH ranges. In an effort to develop highly active and stable metal-contained catalysts, various approaches have been pursued with an emphasis on metal particle size reduction and doping on carbon-based supports. These techniques enhances the metal-support interactions, originating from the chemical bonding effect between the metal dopants and carbon support and the associated interface, as well as the charge transfer between the atomic metal species and carbon framework. This provides an opportunity to tune the well-defined metal active centers and optimize their activity, selectivity and stability of this type of (electro)catalyst. Herein, recent advances in synthesis strategies, characterization and catalytic performance of single atom metal dopants on carbon-based nanomaterials are highlighted with attempts to understand the electronic structure and spatial arrangement of individual atoms as well as their interaction with the supports. Applications of these new materials in a wide range of potential electrocatalytic processes in renewable energy conversion systems are also discussed with emphasis on future directions in this active field of research.

Efficient Oxygen Reduction Catalysts of Porous Carbon Nanostructures Decorated with Transition Metal Species

“…species, referred to as one nonprecious metal atom coordinated with nitrogen atoms or carbon atoms to form M‐N x ‐C complexes, are considered as main active sites of these catalysts. The structure of M/N‐C sites could be varied from different synthetic methods and precursors, in which M‐N 4 /C is one of the most common structures 124. The anchored metal atoms result in distinct electron distribution in N‐doped carbon support, which can modify the physicochemical properties and electronic structure of the material as high‐efficiency ORR catalyst.…”

Atomically Dispersed Semimetallic Selenium on Porous Carbon Membrane as an Electrode for Hydrazine Fuel Cells

“…[4] In this context, enormous efforts have been devoted towards developing efficient, low-cost anode electrocatalysts for HzOR to replace the costly state-of-the-art platinum (Pt) based nanomaterials, [5][6][7] along with optimizing the electrode fabrication craft. [8,9] Recently,s ingle-atom catalysts,e specially atomically dispersed metals anchored on conductive nitrogen (N)-doped carbons (AMCs), have been intensively studied for numerous applications [10][11][12][13][14][15] because of their maximized atom utilization, unusual electronic structure and intriguing properties that differ from their nanoparticles (NPs) counterpart in terms of that is,improved activity and/or selectivity. [16,17] Although there has been progress in the design of AMCs by pyrolysis of carefully engineered metal/carbon precursors (i.e.m etal-organic frameworks (MOFs), [18] in which metal atoms were coordinated with Na toms and in the form of typical MN n atomic configuration (n represents coordination number), controlling the aggregation of single atoms in carbons during synthesis and in the later utilization remains challenging,b ecause the high surface energy makes them easily aggregate into NPs at high pyrolysis temperature and in complex catalytic reactions,w hich decrease their activity.…”

“…c) CV curves of SeNCM-1000 in 1 m KOH with 100 mm N 2 H 4 at different scan rates(5,10,15,20,40,100 mVs À1 ). b) CV curves of SeNCM-x,S epowder and NCM-1000 for HzOR (100 mm N 2 H 4 ,1m KOH, scan rate 5mVs À1 ).…”

Towards High‐Performance Electrocatalysts for Oxygen Reduction: Inducing Atomic‐Level Reconstruction of Fe‐Nx Site for Atomically Dispersed Fe/N‐Doped Hierarchically Porous Carbon

“…[9] The deliberate investigation of TM-N-C electrocatalysts can be traced back to 1964 when Jasinski found that cobalt phthalo-cyanine exhibited ORR activity in alkaline electrolyte. [13,14] Therefore, the designa nd synthesis of high-performance TM-N-C electrocatalyst still remainsabig challenge. [11,12] Unfortunately,t he pyrolysis of metal-macrocycle compoundsu sually resultsi na nuncontrolled agglomeration of metal-based nanoparticles (NPs) with limited number of active TM-N x moieties and an unfavourable porous structure that hinderst he mass transport of ORR reactants,l eadingt oa ni nferiorO RR activity.…”