Cu Anchored Ti 2 NO 2 as High Performance Electrocatalyst for Oxygen Evolution Reaction: A Density Functional Theory Study

Designing Highly Efficient Electrocatalyst for ORR and OER Based on Nb2CO2 MXene: The Role of Transition Metals and N-Doping Content

Finding efficient and stable electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is imperative for advancing zinc-air batteries. Herein, the effect of transition metal anchored on Nb2CO2 with different N content to form TM-Nx-Nb2CO2 on the catalytic activity of ORR and OER is investigated by density functional theory. Among all the designed TM-Nx-Nb2CO2, Pt-N12.50%-Nb2CO2, Pt-N37.50%-Nb2CO2, Pt-N50.00%-Nb2CO2, Pd-N68.75%-Nb2CO2, and Pd-N100%-Nb2CO2 are excellent ORR electrocatalysts with ηORR values of 0.38, 0.36, 0.38, 0.38, and 0.34 V, respectively. Rh-Nb2CO2, Rh-N12.50%-Nb2CO2, Rh-N31.25%-Nb2CO2, Rh-N37.50%-Nb2CO2, Rh-N50.00%-Nb2CO2, Pt-N50.00%-Nb2CO2, Rh-N68.75%-Nb2CO2, and Rh-N81.25%-Nb2CO2 are excellent OER electrocatalysts with ηOER values of 0.33, 0.37, 0.34, 0.36, 0.37, 0.34, 0.38, and 0.33 V, respectively. Notably, Rh-Nb2CO2 and Pt-N50.00%-Nb2CO2 exhibit outstanding ORR and OER bifunctional catalytic activity with potential gap values of 0.80 and 0.72 V, respectively, which are higher than the activities of most reported bifunctional catalysts. Furthermore, electronic structure analysis indicates that the moderate adsorption strength of oxygen-containing intermediates on active centers is crucial for achieving highly active bifunctional catalysts for ORR and OER. This study provides a strategy for the design of novel ORR and OER catalysts using 2D MXene materials.

Constructing highly efficient bifunctional catalysts for oxygen reduction and oxygen evolution by modifying MXene with transition metal

Exploring highly active electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has become a growing interest in recent years. Herein, an efficient pathway for designing MXene-based ORR/OER catalysts is proposed. It involves introducing non-noble metals into Vo (vacancy site), H1 and H2 (the hollow sites on top of C and the metal atom, respectively) sites on M2CO2 surfaces, named TM-VO/H1/H2-M2CO2 (TM = Fe, Co, Ni, M = V, Nb, Ta). Among these recombination catalysts, Co-H1-V2CO2 and Ni-H1-V2CO2 exhibit the most promising ORR catalytic activities, with low overpotential values of 0.35 and 0.37 V, respectively. Similarly, Fe-H1-V2CO2, Co-VO-Nb2CO2, and Ni-H2-Nb2CO2 possess low OER overpotential values of 0.29, 0.39, and 0.44 V, respectively, suggesting they have enormous potential as effective catalysts for OER. Notably, Co-H2-Ta2CO2 possesses the lowest potential gap value of 0.53 V, demonstrating it has an extraordinary bifunctional catalytic activity. The excellent catalytic performance of these recombination catalysts can be elucidated through an electronic structure analysis, which primarily relies on the electron-donating capacity and synergistic effects between transition metals and sub-metals. These results provide theoretical guidance for designing new ORR and OER catalysts using 2D MXene materials.

Reasonable Design of MXene-Supported Dual-Atom Catalysts with High Catalytic Activity for Hydrogen Evolution and Oxygen Evolution Reaction: A First-Principles Investigation

MXene-supported single-atom catalysts (SACs) for water splitting has attracted extensive attention. However, the easy aggregation of individual metal atoms used as catalytic active centers usually leads to the relatively low loading of synthetic SACs, which limits the development and application of SACs. Herein, by performing first-principles calculations for Pt and 3d transition metal single atoms immobilized on a two-dimensional (2D) Mo₂TiC₂O₂ MXene surface, we systematically studied the performance of heterogeneous dual-atom catalysts (h-DACs) in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Significantly, h-DACs exhibit higher metal atom loading and more flexible active sites compared to SACs. Benefiting from these features, we found that Pt/Cu@Mo₂TiC₂O₂ heterogeneous DACs exhibits excellent HER activity with ultra-low overpotential |ΔG_H^∗| (0.04 eV), lower than the corresponding Pt@Mo₂TiC₂O₂ (0.14 eV) and Cu@Mo₂TiC₂O₂ (0.33 eV) SACs, and even lower than that of Pt (0.09 eV). Meanwhile, Pt/Ni@Mo₂TiC₂O₂ exhibits superior OER activity with ultra-low overpotential η^OER (0.38 V), lower than that of Pt@Mo₂TiC₂O₂ (1.11 V) and Ni@Mo₂TiC₂O₂ (0.57 V) SACs, and even lower than that of RuO₂ (0.42 V) and IrO₂ (0.56 V). Our finding paves the way for the rational design of h-DACs for HER and OER with excellent activity, which provides guidance for other catalytic reactions.

Embedding Group VIII Elements into a 2D Rigid pc-C3N2 Monolayer to Achieve Single-Atom Catalysts with Excellent OER Activity: A DFT Theoretical Study

Under DFT calculations, a systematic investigation is carried out to explore the structures and oxygen evolution reaction (OER) catalytic activities of a series of 2D single-atom catalyst (SAC) systems, which are constructed by doping the transition metal (TM) atoms in group VIII into the cavities of rigid phthalocyanine carbide (pc-C₃N₂). We can find that when Co, Rh, Ir and Ru atoms are doped in the small or large cavities of a pc-C₃N₂ monolayer, they can be used as high-activity centers of OER. All these four new TM@C₃N₂ nanostructures can exhibit very low overpotential values in the range of 0.33~0.48 V, even smaller than the state-of-the-art IrO₂ (0.56 V), which indicates considerably high OER catalytic activity. In particular, the Rh@C₃N₂ system can show the best OER performance, given that doped Rh atoms can uniformly serve as high-OER-active centers, regardless of the size of cavity. In addition, a detailed mechanism analysis was carried out. It is found that in these doped pc-C₃N₂ systems, the number of outer electrons, the periodic number of doped TM atoms and the size of the embedded cavity can be considered the key factors affecting the OER catalytic activity, and excellent OER catalytic performance can be achieved through their effective cooperation. These fascinating findings can be advantageous for realizing low-cost and high-performance SAC catalysts for OER in the near future.

Recent Status and Challenges in Multifunctional Electrocatalysis Based on 2D MXenes

Due to their chemical and electrical characteristics, such as metallic conductivity, redox-activity in transition metals, high hydrophilicity, and adjustable surface properties, MXenes are emerging as important contributors to oxygen reduction...

1 T-MoSe2 monolayer supported single Pd atom as a highly-efficient bifunctional catalyst for ORR/OER

The development of highly-efficient catalysts for oxygen reduction reaction (ORR) or oxygen evolution reaction (OER) is highly crucial for the commercial applications of some novel energy-related devices. Herein, using comprehensive first-principles computations, the potential of a variety of single metal-based catalysts supported by MoSe₂ nanosheet to boost the ORR or OER process was evaluated. The computations revealed that these considered metal atoms can be more stably anchored on 1 T-MoSe₂ than those of on 2H-MoSe₂. In particular, the supported Ni and Pd catalysts on 1 T-MoSe₂ exhibit high OER activity due to their quite low overpotential (0.47 and 0.49 V). Meanwhile, the anchored Pd atom on 1 T-MoSe₂ also displays excellent ORR performance with an ultra-low overpotential of 0.32 V, thus implying its superior bifunctional activity for ORR/OER. Our results provide a quite promising avenue to design a new class of MoSe₂-based single atom catalysts for fuel cells, which also further enriches the application fields of MoSe₂ nanosheets in advanced catalysis.

MXenes as Superexcellent Support for Confining Single Atom: Properties, Synthesis, and Electrocatalytic Applications

Single atom catalysts (SACs) have shown their noticeable potential and gradually become a new favorite in catalytic field due to the particular selectivity, high catalytic performance, and strong durability. The most important factor in the synthesis of SACs is the selection of appropriate support and formation of metal-support interaction. Among a large number of nanomaterials, MXenes can be utilized as benign supports for fixing SACs because of their expansive specific surface area, regulable bandgap, superior electronic conductivity, and strong mechanical stability. The structure and property of MXenes can be manipulated by changing transition metal elements and surface termination. Here, the uniqueness and superiority of MXenes as superexcellent supports for confining SACs are analyzed from structure and property. The synthetic strategy of MXene-supported SACs is also summarized, especially emphasizing the immobilization of isolated atom against aggregation by utilizing the formidable metal-support covalent coordination interaction. In addition, the applications of MXene-supported SACs in electrocatalytic field are highlighted, including hydrogen evolution reaction, oxygen evolution reaction, overall water splitting, oxygen reduction reaction, and nitrogen reduction reaction. Finally, the challenges and prospects are pointed out for the further understanding and practical application of MXene-supported SACs in electrocatalysis.