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We present a novel in situ liquid-cell transmission electron microscopy (TEM) approach to study the behavior of metal nanoparticles under high-energy electron irradiation. By utilizing a radically-inert liquid environment, we aim to minimize radiolysis effects and explore the influence of charge-induced transformations. We observed complex dynamics in nanoparticle behavior, including morphological changes and transitions between amorphous and crystalline states. These transformations are attributed to the delicate interplay between charge accumulation on the nanoparticles and enhanced radiolysis, suggesting a significant role for charge-assisted processes in nanoparticle evolution. Our findings provide valuable insights into the fundamental mechanisms driving nanoparticle behavior at the nanoscale and demonstrate the potential of liquid-cell TEM for studying complex physicochemical processes in controlled environments.

Abstract Transition metal hydroxides (TM(OH)2) have drawn significant attention for their potential applications in the environmental and energy field. In this study, we investigated the phase transition of cobalt hydroxide (Co(OH)2) under electron beam irradiation using in situ high-resolution transmission electron microscopy. Both the α- and β-Co(OH)2 phases underwent a phase transition to a spinel Co3O4 phase, forming nanograins with a porous morphology. However, the α-Co(OH)2 showed a faster phase transition and dramatic volume shrinkage during the phase transition. Our results provide a detailed explanation of the mechanism behind the deterioration of the layered structure and the emergence of defects during the phase transition.

Stable electrodes are crucial for the practical applications of electrochemical systems. In this study, we report a simple method for synthesizing three-dimensional glassy-like carbon (3D·GC) on an alumina substrate through pyrolysis of benzyl alcohol and applying it to electrocatalytic reactions. Given its distinctive 3D morphology and stability in aqueous solution, the 3D·GC electrode exhibits significantly higher electrocatalytic activity than the commercial GC. Moreover, the rough surface of the 3D·GC electrode is favorable for direct immobilization of catalytic sites, such as metals (Au and Ag) and single-atom catalysts. The developed method for immobilizing single Ni sites is successfully applied to the 3D·GC electrode, resulting in the Ni SAC-3D·GC electrode that exhibits high CO selectivity and durability for electrochemical CO2 reduction. The Faradaic efficiency of CO is over 90% across a wide potential range. Due to direct immobilization, the Ni SAC-3D·GC electrode shows remarkable stability even after multiple reuse cycles, indicating its potential for long-term electrocatalytic applications. To gain an understanding of the mechanism underlying the high CO selectivity during CO2 reduction, the theoretical interactions between the individual Ni sites and the carbon substrate are explored. This theoretical analysis highlights the crucial role of the carbon substrate in stabilizing the COOH intermediate for electrochemical CO2 reduction under neutral conditions.

Cobalt hydroxides, Co(OH)2, have attracted considerable attention due to their diverse applications in the fields of energy and the environment. However, probing the electronic structure of Co(OH)2 is challenging, mainly due to its sensitivity to electron beam irradiation. In this study, we report the unperturbed O K-edge and Co L-edge for Co(OH)2 by electron beam damage and investigate the electronic structure transformation of Co(OH)2 under electron beam irradiation, using low current electron energy loss spectroscopy. In particular, the O K-edge pre-peak at 530 eV, which is not found in the undamaged Co(OH)2, begins to appear with an increasing electron beam current. In addition, the Co L-edge peak shifts to a higher energy, close to Co3O4, indicating that the localized phase transition within Co(OH)2 leads to the formation of Co3O4.