Flash Bottom‐Up Arc Synthesis of Nanocarbons as a Universal Route for Fabricating Single‐Atom Electrocatalysts

Abstract

Atomically dispersed metal atoms on supporting materials inherit the merits of both heterogeneous and homogeneous catalysts, such as the easy separation and high durability of a heterogeneous phase and the well-structured catalytic active sites and tunable activity of a homogeneous phase. [6][7][8] The isolated metals in SACs are located on neighboring surface atoms (metal oxide, metal nitride, and carbon atoms) or coordinated with heteroatoms, such as nitrogen, sulfur, and phosphorus. [7,[9][10][11] The metal centers and their surrounding atoms can be thought of as molecular catalytic sites that proceed down a highly selective reaction pathway. [12][13][14][15][16] For a decade, a variety of synthesis strategies have been developed to realize highly active SACs. [7,[17][18][19] One of the most widely applied methods is the defect engineering strategy. [1,[20][21][22] Preformed defects on supporting materials can alter the surrounding electronic state and have been used as effective "traps" to capture metal precursors and anchor metal atoms during post-treatment. [8,23] Another popular synthetic method is the spatial confinement strategy. Despite considerable development in the field of single-atom catalysts (SACs)on carbon-based materials, the reported strategies for synthesizing SACs generally rely on top-down approaches, which hinder achieving both simple and universal synthesis routes that are simultaneously applicable to various metals and nanocarbons. Here, a universal strategy for fabricating nanocarbon based-SACs using a flash bottom-up arc discharge method to mitigate these issues is reported. The ionization of elements and their recombination process during arc discharge allows the simultaneous incorporation of single metal atoms (Mn, Fe, Co, Ni, and Pt) into the crystalline carbon lattice during the formation of carbon nanohorns (CNHs) and N-doped arc graphene. The coordination environment around the Co atoms of Co 1 /CNH can be modulated by a mild post-treatment with NH 3 . As a result, Co 1 /CNH exhibits good oxygen reduction reaction activity, showing a 1.92 times higher kinetic current density value than the commercial Pt/C catalyst in alkaline media. In a single cell experiment, Co 1 /CNH exhibits the highest maximum power density of 472 mW cm −2 compared to previously reported nonprecious metal-based SACs.

Recent Advances in Graphene-Based Single-Atom Photocatalysts for CO2 Reduction and H2 Production

“…For example, Jung et al [91] developed a bo om-up arc-discharge technique to create single-atom catalysts (SACs) by using nanocarbon materials, as seen in Figure 5. This unique technique enables the integration of different metal atoms, including Co, Ni, Mn, Fe, and Pt, into the crystalline carbon structure.…”

Recent advances in carbon-supported non-precious metal single-atom catalysts for energy conversion electrocatalysis

“…Finally, the metal atoms' high dispersion and high loading are realized. Single atoms of various metal centers have been achieved in this way, such as the synthesis of Ni-N-C moieties supported on carbon black by current heating (Figure 7A) [112], single atomic transition metals (Co, Ni, Cu) embedded in nitrogen-doped graphene by two-second microwave heating (Figure 7B) [113], Co-P SACs based on highly conductive multiwall CNTs by pulsed laser confinement (PLC) operation (Figure 7C) [114], mono-dispersed Mn, Fe, Co, and Ni atom trapped in the crystalline carbon lattice of N-doped graphene by arc discharge (Figure 7D) [115]. Ultrafast synthesis has a unique advantage in the research and development of monatomic materials due to the high utilization of energy and time, which provides a new idea for the large-scale production of NPM-SACs/CS.…”

Single–atom catalysts based on Fenton-like/peroxymonosulfate system for water purification: design and synthesis principle, performance regulation and catalytic mechanism

“…The conditions in the “bottom-up” methods need to be accurately controlled, and the metal loading of the prepared catalyst is usually substantially lower than that of the starting precursor because it is difficult to disperse and stably form a single metal atom in the key post-treatment process of removing mononuclear metal complexes. 40,41 The “top-down” route usually accelerates the thermal movement of metal atoms under sufficient energy (high temperature), reaches the fracture of metal–metal bonds existing in metal nanoparticles or bulk metals, and makes a strong interaction between the escaped isolated metal species and the anchor point for the preparation of stable and completely dispersed SACs. 42–45…”