New Folding 2D‐Layered Nitro‐Oxygenated Carbon Containing Ultra High‐Loading Copper Single Atoms

Abstract

merits from both homogenous catalysts such as high atomic utilization efficiency and uniform active sites, and of heterogeneous catalysts, namely good stability, facile separation, and regeneration altogether. [1] Moreover, down-sizing metal particles to an atomically-dispersed form greatly increases the surface energy of the metals, resulting in pronounced catalytic reactivity. [2] Both theoretical and experimental investigations reveal the unusually high catalytic performance of SACs over conventional and nanoparticle-based catalysts in a multitude of key chemical reactions. [3][4][5][6][7][8][9] However, complicated preparation methods and limited exposure of active sites are the important challenges hindering them from widespread applications. SAC synthesis usually relies on multi-step techniques such as MOFderived synthesis, [10,11] ligand chelation, [12] defect creation, [13] frozen dry, [14] and light irradiation. [15] For example, the most commonly-used technique to prepare SACs on carbon supports such as MOF-derived synthesis usually needs sacrificial MOF templates before doping with the target metals, subsequential pyrolysis/carbonization, and leaching of the sacrificial metals in MOFs to finally obtain SACs on carbon supports. [11,[16][17][18] Other high precisive methods to prepare SACs such as ion bombardment, [19] mass-selected soft landing, and atomic layer deposition [20][21][22] also rely on using sophisticated instruments or expensive precursors that are not affordable or scalable in general laboratories.In addition, to fully gain well-isolated atoms, the number of metals loaded onto the supporting materials need to be extremely low. In general, <5 wt.% of metal can be anchored on the support matrixes in an atomically-dispersed feature, due to intrinsically high surface energy. [23][24][25] When a higher amount of metals was tried to load, clusters and nanoparticles are usually formed due to Oswald ripening. [26,27] Moreover, although recently developed techniques may increase the metal loading up to >5 wt.%, unfortunately, most of metal sites derived from those methods are buried inside the carbon frameworks. Thin 2D nanomaterials could be an ideal substrate to maximize the exposure of active sites to reactants. Hence, great efforts have been dedicated to anchoring single metal atoms onto 2DThe discoveries of 2D nanomaterials have made huge impacts on the scientific community. Their unique properties unlock new technologies and bring significant advances to diverse applications. Herein, an unprecedented 2D-stacked material consisting of copper (Cu) on nitro-oxygenated carbon is disclosed. Unlike any known 2D stacked structures that are usually constructed by stacking of separate 2D layers, this material forms a continuously folded 2D-stacked structure. Interestingly, advanced characterizations indicate that Cu atoms inside the structure are in an atomically-dispersed form with extraordinarily high Cu loading up to 15.9 ± 1.2 wt.%, which is among the highest reported metal loading for single-ato...

General Pyrolysis for High-Loading Transition Metal Single Atoms on 2D-Nitro-Oxygeneous Carbon as Efficient ORR Electrocatalysts

“…Then, the mixture was placed in a quartz boat that was closed with a lid and pyrolyzed at 800 °C (ramp rate = 10 °C·min –1 ) in a tube furnace under an Ar atmosphere (flow rate = 200 sccm). Note that metal loading contents can be adjusted by tuning the ratios of M-Phc:Dicy:urea as described in detail in our previous report . Basically, urea tends to carry a higher metal loading than Dicy, as it is a smaller molecule with high N and O contents that are beneficial for anchoring isolated metal atoms.…”

“…Therefore, the ratio between M-Phc:Dicy:urea should be optimized to achieve high metal loading and well-exfoliated 2D nanosheets. For example, 15.9 wt % Cu loading content with a suitably exfoliated 2D structure could be achieved when the weight ratio of M-Phc:Dicy:urea of 1:5:5 was used . Nevertheless, some metals are supposed to form clusters more easily than the others, depending on the nature of the metals.…”

Atomic‐Level Regulation of Cu‐Based Electrocatalyst for Enhancing Oxygen Reduction Reaction: From Single Atoms to Polymetallic Active Sites

“…[48] Copyright 2019, American Chemical Society; Reproduced with permission. [49] Copyright 2022, Wiley-VCH. pyrolysis method.…”

“…Cu-N/PC has excellent ORR catalytic activity with an E 1/2 of 0.91 V (vs RHE) in 0.1 m KOH solution (Figure 3d). Butburee et al [49] reported for the first time a new class of Cu-based SACs (F2DS-Cu) with a new 2D layered nanostructure. Cu-based SACs with high Cu loading (15.9 wt%) were obtained by one-step pyrolysis of a mixture of copper phthalocyanine (CuPc), urea, Reproduced with permission.…”

Precise Design and Modification Engineering of Single‐Atom Catalytic Materials for Oxygen Reduction

“…[253,254] The study of highloading single atoms is of great significance for improving the performance of ORR catalysts, understanding the catalytic mechanism, and promoting its application. [164,255,256] For example, Yamauchi developed a Fe-N 4 SACM with 8.36 wt.% metal loading using the molten salt exfoliation method to anchor Fe-N 4 on ultrathin 2D graphene with abundant defects. [257] Xu et al synthesized a SACM of 14.0 wt.% Co loading by a sacrificial template strategy with layered g-C 3 N 4 as a sacrificial template.…”