Single‐Atom Sites on MXenes for Energy Conversion and Storage

Abstract

Single‐atom sites on MXenes (SASs‐MXenes) have attracted widespread attention for energy storage and conversion due to their highest atom utilization efficiency, intriguing intrinsic properties, unusual performance, and improved robustness. In addition, the large surface area and abundant anchor sites make MXenes ideal substrates for supporting single atoms via covalent interaction. Herein, the main strategies for synthesis of SASs‐MXenes are first summarized, which cover capturing single atoms by cation vacancies, coordinating single atoms with heterodopants, and inheriting single atoms from MAX phases. Then, disclosing the crucial roles SASs‐MXenes play in tuning the kinetics and thermodynamics of various catalytic reactions, i.e., hydrogen evolution reaction, nitrogen reduction reaction, CO2 reduction reaction, CO2 functionalization, polysulfide conversion, and other redox reactions involved in rechargeable batteries, is focused on. Finally, the challenges and future opportunities for developing highly active SASs‐MXenes are discussed.

Energy‐Saving Hydrogen Production by Seawater Electrolysis Coupling Sulfion Degradation

“…For SOR on CoS 2 (100) and ( 111 The Ti 3 C 2 T x MXene also contributes greatly to improving the interfacial properties of CoS 2 @C/MXene/NF for boosting SOR although it is not the active phase. [34,35] Their large surface with abundant polar groups (e.g., -OH and -O) enables uniform anchoring of nanosheet networks to expose more active phases, thereby expanding the ECSA of the electrode (Figure S22, Supporting Information). A similar effect is also observed for HER on CoO-based electrodes (Figure S23, Supporting Information).…”

Roles of Metal Ions in MXene Synthesis, Processing and Applications: A Perspective

“…First, MXene‐supported single metal atom catalysts (SACs@MXene) can be synthesized by anchoring metal atoms in cation vacancies or surface groups. [ 30 , 91 , 175 , 176 , 177 , 178 ] Zhao et al. synthesized a Pt 1 /Ti 3‐ x C 2 T y single‐atom catalyst by mixing a [PtCl 6 ] 2− solution with a MXene (Ti 3‐ x C 2 T y ) suspension, and no additional reduction operation was needed ( Figure 11 a ).…”

“…Because of the redox activities of metal ions and MXenes, MXene sheets with anchored metal atoms or nanoparticles can be synthesized in a one‐step method. [ 30 , 31 ] The evolution from MAX to MXene also involves metal ions, such as A x + oxidized from the A atoms in MAX by etchants, examples being Li + in the LiF/HCl route and Cu 2+ in the molten CuCl 2 route. Considering that the quality of MXene sheets highly depends on the preparation process (including the etching reaction and delamination), it is vital to figure out the role of metal ions in MXene synthesis and the interactions between them.…”

Single‐Atom Fe Catalysts for Fenton‐Like Reactions: Roles of Different N Species

“…[11][12][13][14] SACs have been found to be very favorable in many fields, including electrocatalysis, [15][16][17][18] organocatalysis, [19][20][21] industrial catalysis, [22][23][24] and others. [25][26][27][28][29][30] Consequently, revealing the atomic structure of the central metal atoms and the SMSI in SACs has become an important subject of research because it provides possibilities for rational design of novel SACs for specific reactions. The recent development of advanced characterization techniques, including aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM), scanning tunneling microscopy images, extended X-ray absorption fine structure (EXAFS) curve fitting, and DFT modeling, provide crucial tools for identifying the atomic structure.…”