Phase Engineering and Synchrotron-Based Study on Two-Dimensional Energy Nanomaterials

Abstract

In recent years, there has been significant interest in the development of twodimensional (2D) nanomaterials with unique physicochemical properties for various energy applications. These properties are often derived from the phase structures established through a range of physical and chemical design strategies. A concrete analysis of the phase structures and real reaction mechanisms of 2D energy nanomaterials requires advanced characterization methods that offer valuable information as much as possible. Here, we present a comprehensive review on the phase engineering of typical 2D nanomaterials with the focus of synchrotron radiation characterizations. In particular, the intrinsic defects, atomic doping, intercalation, and heterogeneous interfaces on 2D nanomaterials are introduced, together with their applications in energy-related fields. Among them, synchrotron-based multiple spectroscopic techniques are emphasized to reveal their intrinsic phases and structures. More importantly, various in situ methods are employed to provide deep insights into their structural evolutions under working conditions or reaction processes of 2D energy nanomaterials. Finally, conclusions and research perspectives on the future outlook for the further development of 2D energy nanomaterials and synchrotron radiation light sources and integrated techniques are discussed.

Strategies to alleviate distortive phase transformations in Li-ion intercalation reactions: an example with vanadium pentoxide

“…124,125 These work illustrated the structural dynamics of host upon (de) intercalation, 47,69,126 and we refer the readers to review papers focusing on the advanced synchrotron techniques. 121 Advanced apparatus revealed phase transformations at high temporal or spatiotemporal resolution, such as AMPIX cell (Argonne's multi-purpose in situ X-ray cell) that applies uniform stack pressure for various X-ray scattering and spectroscopic measurements to be performed in operando with high temporal resolution. 47,127 Synchrotron-based microscopy methods such as scanning transmission X-ray microscopy (STXM) can collect near-edge fine structure with sub-micron resolution for both chemically (de)lithiated samples and samples from electrochemically (de)lithiated and disassembled coin cells.…”

“…Operando and series of ex situ powder X-ray diffraction can provide information on the phase transformation pathways of electrode materials at the lattice level. 121 However, its ability to directly image the positions of low-Z atoms and resolve their site occupancies, which is crucial for extrapolating Li diffusion pathways, is limited, with exceptions corroborated by neutron diffraction. In contrast, single-crystal X-ray diffraction with a Mo target ( λ = 0.71 Å), typically used for identifying molecular single crystals, provides precise determination of low-Z atoms at the Angstrom level by accurately mapping their electron densities.…”

How Amorphous Nanomaterials Enhanced Electrocatalytic, SERS, and Mechanical Properties

“…In addition to the direct synthesis of amorphous nanomaterials to promote the existing electrocatalytic activity of crystalline counterparts, the in situ self-reconstruction of amorphous species produced from the crystal during catalysis has been found to be a key to electrocatalysis . It is widely believed that, even for a crystal catalyst, the reconstructed amorphous structure is considered to be the real active phase that is advantageous to the catalytic process. − Thus, amorphization could also bring new properties to inactive traditional crystal materials. For example, unlike the layered hydroxides, which are well-known to be excellent active materials for the OER, some lamellar materials show poor intrinsic activity and electronic conductivity, resulting in inferior catalytic performance.…”

“… 41 It is widely believed that, even for a crystal catalyst, the reconstructed amorphous structure is considered to be the real active phase that is advantageous to the catalytic process. 42 − 44 Thus, amorphization could also bring new properties to inactive traditional crystal materials. For example, unlike the layered hydroxides, which are well-known to be excellent active materials for the OER, some lamellar materials show poor intrinsic activity and electronic conductivity, resulting in inferior catalytic performance.…”

Identification of Synergies in Fe, Co-Coordinated Polyphthalocyanines Scaffolds for Electrochemical CO2 Reduction Reaction

“…In fact, the precise development and implementation of SACs often face a significant obstacle due to the excessive emphasis on the catalytic sites themselves, while neglecting the platforms that host them. − This research ambiguity arises from two main factors. First, the uncertainty surrounding the catalyst structure and the heterogeneous nature of the catalytic sites contribute to the issue.…”