Rational Design of Single‐Atom Site Electrocatalysts: From Theoretical Understandings to Practical Applications

Abstract

inflicting the foreign potential. Up to now, the state-of-the-art electrocatalysts mainly depend on the noble-metal-based catalysts, such as platinum (Pt), Palladium (Pd), ruthenium (Ru), Iridium (Ir), rhodium (Rh), and gold (Au). [1,2] While the high cost and low storage of noble-metals compel the sluggish pullulation of electrocatalytic applications. [3] The avenues to overcome this bottleneck issue mainly include two aspects. One strategy is to seek a promising substituendum with superior catalytic activity to replace the traditional noble-metal catalysts. Based on this strategy, enormous breakthroughs have been reported via modulating the macroscopic physical and chemical properties, such as shape, structure, size, crystal face, and composition. [4][5][6][7][8][9][10][11][12][13] Another strategy is to minimize the usage of noble-metals without weakening electrocatalytic performance. In comparison with the conventional bulk catalysts, reducing the usage of noble metal via downsizing the particles to clusters or even the single atoms can trigger the immeasurably electrocatalytic performance based on the site isolation effect and size effect, as illustrated in Figure 1. [14][15][16] The catalytic reactions, involving the heterogeneous and homogeneous, usually occur on the surface of catalysts, of which the serviceable active sites are restricted to small fraction of surface atoms. Thus, isolating the active sites individually to prepare the single-atom site electrocatalysts (SACs) can greatly elevate the atomic utilization. From the microscopic view, although the atomically dispersed metal atoms could present their maximized utilization, the high surface free energy of single atoms suffer from the migration and aggregation. [17,18] Anchoring the single atom on the suitable supports is the key prerequisite for realizing the efficient catalysis. Some compounds, such as metals, metal oxides, metal chlorides/carbides/ nitrides/sulfides, layered double hydroxides (LDHs), and other modified carbon materials, are used as the supports to stabilize the single atoms. [19][20][21] In addition, enormous preparation strategies of stable and high-efficiency electrocatalysts are also presented, such as the impregnation and coprecipitation strategy, spatial confinement strategy, coordination site construction strategy, defect/vacant design strategy, electrochemical method, atomic layer deposition (ALD) method, synthesizing SACs from bulk metals or metal oxide powers, ball-milling method, and so on.Atomically dispersed metal-based electrocatalysts have attracted increasing attention due to their nearly 100% atomic utilization and excellent catalytic performance. However, current fundamental comprehension and summaries to reveal the underlying relationship between single-atom site electrocatalysts (SACs) and corresponding catalytic application are rarely reported. Herein, the fundamental understandings and intrinsic mechanisms underlying SACs and corresponding electrocatalytic applications are systemically summarized. Different ...

Structural revolution of atomically dispersed Mn sites dictates oxygen reduction performance

“…Recently, isolated single-atom sites catalysts (ISASC), featured with the maximized metal atom efficiency and distinct electronic properties, have been considered as the most promising alternatives [8][9][10][11][12][13][14]. Especially, atomically dispersed metal iron or cob-alt supported on nitrogen coordinated carbon (Fe-N-C or Co-N-C) materials generally show their encouraging ORR activity [15][16][17][18][19][20][21].…”

Theoretical Predictions, Experimental Modulation Strategies, and Applications of MXene‐Supported Atomically Dispersed Metal Sites

“…Theoretical methods can be used to predict the electronic structures of the active sites. [34,35] The properties of a series of TiCO materials (belonging to the class of MXenes) with similar structures but characterized by different components or stoichiometric ratios varied from each other. [36] During the synthesis of MXenes, a variety of free ligands are absorbed on the surface of MXenes, resulting in surface functionalization.…”

“…Both pathways can yield the desired results if the selectivity achieved is comparable. [34] The development of highly active ORR catalysts involves the use of Pt-based materials. It is noteworthy that progress has been made in the field of developing TM-based catalysts supported on MXenes.…”

Single-atom catalysts: stimulating electrochemical CO2 reduction reaction in the industrial era

“…Single-atom catalysts (SACs) have encouraged intense research in catalytic chemistry. 12–18 Their active centers exhibit a variation in characteristics with a decrease in the size of the metal catalyst. Alternatively, accompanied by a reduction in the size of their active centers, the surface energies of these catalysts can be significantly enhanced.…”