Liquid-phase catalytic techniques, together with electrocatalytic water splitting, photocatalytic water splitting, and electrocatalytic CO2 discount, have garnered widespread consideration over the previous few many years[1], [2], [3], [4], [5]. In these techniques, the efficiency and stability of energetic websites on the interface between strong catalysts and liquid electrolytes are essential for figuring out the feasibility of scaling up for industrial functions[6]. To comprehensively perceive the response mechanisms of those heterogeneous catalytic reactions, intensive analysis has sought to make the most of numerous in situ spectroscopic characterization strategies, which embody X-ray diffraction (XRD), X-ray absorption effective construction (XAFS), Raman spectroscopy, and Fourier rework infrared spectroscopy (FT-IR)[6], [7], [8], [9], [10], [11]. These strategies allow the monitoring of the dynamic evolution of part constructions, redox pathways, and different microstructural traits of catalysts and reactants, significantly by means of real-time observations throughout the whole response course of. Nonetheless, these spectroscopic evaluation strategies historically replicate the general catalytic adjustments in macroscopic samples, making it difficult to establish the dynamic evolution processes of energetic websites on catalysts or in reactants at nanometer and even atomic scale[3].
The development of transmission electron microscopy (TEM) has established a robust technological platform for investigating the intrinsic constructions of supplies, providing an optimum spatial decision of 0.5 Å[12]. This method additionally facilitates the evaluation of elemental distribution, crystallographic data, valence traits, and even phonon states[13], [14], [15], [16]. Nonetheless, as a result of stringent vacuum necessities for electron beam propagation, the TEM usually requires excessive vacuum of about 10−5 −10−6 Pa. Nonetheless, the saturated vapor stress (SVP) of conventional liquid supplies is comparatively excessive. As an illustration, the SVP of water at 25 °C is 3.2 kPa. When a drop of liquid water is launched right into a transmission electron microscope (TEM), it rapidly vaporizes as a result of motion of the pumping system, which hinders the direct imaging and detection of liquid or gas-phase samples. Though the arrival of environmental TEM with a differential pumping system can cut back the fuel stress to beneath 10 Torr[17], this vacuum continues to be inadequate to keep up liquid samples throughout the TEM chamber.
With the fast development of micro-nano fabrication expertise, researchers have efficiently encapsulated liquid part samples inside sealed silicon/carbon-based cells and built-in them into the TEM specimen holder, which may sufficiently isolate the liquid part samples from the excessive vacuum surroundings throughout the micro-chamber[18], [19], [20], [21], [22], [23]. Because the expertise progressing, the liquid cell has regularly transitioned from a sealed state to a state of liquid circulate. The incorporation of electrodes, optical fibers, and resistance wires has enabled LP-TEM to simulate a variety of sensible liquid-phase chemical reactions, significantly within the realms of electrocatalysis and photocatalysis[24], [25], [26]. It needs to be identified that, elucidating the evolution of energetic websites on the solid-liquid interface is likely one of the most important points in catalytic reactions, using Liquid-Section Transmission Electron Microscopy (LP-TEM) to analyze these techniques is especially important[27]. This evaluation goals to supply an in depth overview of the present functions of LP-TEM within the fields of electrocatalysis and photocatalysis, offering cutting-edge insights for in situ TEM research of liquid-phase catalytic reactions.
