Interface engineering of transition metal-nitrogen-carbon by graphdiyne for boosting the oxygen reduction/evolution reactions: A computational study

Modulating the electronic structure of graphdiyne-based nanomaterials for engineering nano-bio interfaces in biomedical applications

Graphdiyne (GDY), a two-dimensional (2D) carbon allotrope featuring a unique electronic structure, has attracted considerable attention due to its outstanding properties and potential applications in various fields, particularly in biomedicine due to its exceptional surface area, tunable electronic structure, and biocompatibility. Although promising, this field is still in the proof-of-concept stage due to incomplete understanding of the effects of structural regulation, particularly electronic structure, of GDY-based nanomaterials on their nano-bio interfaces, which seriously hinders the research of GDY-based nanomaterials in the biomedical field. To provide a comprehensive understanding of the relationship between electronic structures and nano-bio interfaces, this review focuses on the modulation of the electronic structure of GDY-based nanomaterials and its implications for engineering nano-bio interfaces for biomedical applications. Firstly, we delve into the intrinsic electronic properties of GDY, including its bandgap tunability and high carrier mobility, which are critical for its functionality in biomedical applications. We then discuss strategies for modulating these properties through oxidation, nonmetallic doping, covalent modification, and metal loading, aiming to optimize the electronic structure of GDY-based nanomaterials for superior performance in specific biomedical contexts, such as biomedical imaging, surface and interface catalysis, free radical scavenging, and drug delivery. Furthermore, we provide an overview of the methodologies for the investigation of these electronic properties, including theoretical simulation, characterization techniques, and real-time analysis of electron transfer at the nano-bio interfaces, highlighting their roles in advancing our understanding and guiding the design of novel GDY-based materials. Finally, this review provides an outlook on future research directions aimed at further optimizing the design of GDY-based nanomaterials and nano-bio interfaces, emphasizing the need for interdisciplinary collaboration to overcome current challenges and to fully realize the potential of GDY-based nanomaterials in biomedical applications. These principles are anticipated to facilitate the future development and clinical translation of precise, safe, and effective nanomedicines with intelligent theranostic features.

Descriptor for electro-oxidation of glycerol with high-efficiency bifunctional Cu-Nx single atom catalyst and coupled with hydrogen evolution/carbon dioxide reduction

Electrochemical glycerol oxidation reaction (GOR) presents a promising approach for converting excess glycerol (GLY) into high-value-added products. However, the complex mechanism and the challenge of achieving selectivity for diverse products make GOR difficult to address in both experimental and theoretical studies. In this work, three nitrogen-doped graphene-supported copper single-atom catalysts (CuNx@Gra SACs, x = 2-4) were selected as the model system due to their simple structure, excellent conductivity and high structural stability. Density functional theory (DFT) calculations were employed to gain deeper insight into the catalytic mechanism. The DFT results revealed that both CuN2@Gra and CuN3@Gra follow the same optimal pathway, leading to the formation of formic acid as a key product. The GOR activity and selectivity of CuNx@Gra catalysts follow the trend CuN3@Gra > CuN2@Gra > CuN4@Gra. Subsequent microkinetic analysis, based co on the DFT-derived energetics, confirmed this predicted activity sequence. The GOR activity determined by the limiting potential (UL) is correlate well with changes in the adsorption free energy (ΔGGLY*), the d-band centers of axial dz2 orbitals (εdz2) and integrated crystal orbital Hamilton population (ICOHP). Notably, the simple descriptor ΔGGLY* exhibits a good linear correlation with the free energies of other adsorbates, clarifying the conversion relationships between reaction intermediates and simplifying the understanding of reaction complexity. Moreover, computational results indicate that CuN2@Gra and CuN3@Gra systems can serve as both anode catalysts (for GOR) and cathode catalysts (CO2 reduction for CuN2@Gra and H2 evolution for CuN3@Gra). This study offers insights for designing efficient electrocatalysts, enhancing GLY utilization.

Nitrogen, sulfur co-coordinated iron single-atom catalysts with the optimized electronic structure for highly efficient oxygen reduction in Zn-air battery and fuel cell

Atomically dispersed iron-nitrogen-carbon (FesbndNsbndC) materials have been considered ideal catalysts for the oxygen reduction. Unfortunately, designing and adjusting the electronic structure of single-atom Fe sites to boost the kinetics and activity still faces grand challenges. In this work, the coordination environment engineering is developed to synthesize the FeSA/NSC catalyst with the tailored N, S co-coordinated Fe atomic site (Fe-N3S site). The structural characterizations and theoretical calculations demonstrate that the incorporation of sulfur can optimize the charge distribution of Fe atoms to weaken the adsorption of OH* and facilitate the desorption of OH*, thus leading to enhanced kinetics process and intrinsic activity. As a result, the S-modified FeSA/NSC exhibits outstanding catalytic activity with the half-wave potentials (E1/2) of 0.915 V and 0.797 V, as well as good stability, in alkaline and acidic electrolytes, respectively. Impressively, the excellent performance of FeSA/NSC is further confirmed in Zn-air batteries (ZABs) and fuel cells, with high peak power densities (146 mW cm-2 and 0.259 W cm-2).

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.