This review presents an overview of the application of electrochemical liquid-phase transmission electron microscopy (ELP-TEM) in visualizing rechargeable battery reactions. The technique provides atomic-scale spatial resolution and real-time temporal resolution, enabling direct observation and analysis of battery materials and processes under realistic working conditions. The review highlights key findings and insights obtained by ELP-TEM on the electrochemical reaction mechanisms and discusses the current limitations and future prospects of ELP-TEM, including improvements in spatial and temporal resolution and the expansion of the scope of materials and systems that can be studied. Furthermore, the review underscores the critical role of ELP-TEM in understanding and optimizing the design and fabrication of high-performance, long-lasting rechargeable batteries.

The present study describes the development of a potentiometric sensor for microbial monitoring in water based on catalase activity. The sensor comprises a MnO2-modified electrode that responds linearly to hydrogen peroxide (H2O2) from 0.16 M to 3.26 M. The electrode potential drops when the H2O2 solution is spiked with catalase or catalase-producing microorganisms that decompose H2O2. The sensor is responsive to different bacteria and their catalase activities. The electrochemical sensor exhibits a lower limit of detection (LOD) for Escherichia coli at 11 CFU/ml, Citrobacter youngae at 12 CFU/ml, and Pseudomonas aeruginosa at 23 CFU/ml. The sensor shows high sensitivity at 3.49, 3.02, and 4.24 mV/cm2dec for E. coli, C. youngae, and P. aeruginosa, respectively. The abiotic sensing electrode can be used multiple times without changing the response potential (up to 100 readings) with a shelf-life of over six months. The response time is a few seconds, with a total test time of 5 min. Additionally, the sensor effectively tested actual samples (drinking and grey water), which makes it a quick and reliable sensing tool. Therefore, the study offers a promising water monitoring tool with high sensitivity, stability, good detection limit, and minimum interference from other water contaminants.

Water splitting is a long-standing quest to material research for mitigating the global energy crisis. Despite high efficiency shown by several high cost noble metal containing electrocatalysts in the water splitting reaction, scientists are focused on alternate metal-free carbon or polymer based materials with comparable activity to make the process economical. In this article, we have strategically designed a noble metal-free thiadiazole (TDA) and triazine (Trz) linked porous organic polymer (TDA-Trz-POP) having N- and S-rich surface. Powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR), solid state 13C magic angle spinning nuclear magnetic resonance (MAS-NMR) and X-ray photoelectron spectroscopic (XPS) analyses have been performed to predict its probable framework structure. This scrunch paper type TDA-Trz-POP shows an extravagant potential for the hydrogen evolution reaction (HER) with a low overpotential (129.2 mV w.r.t. RHE for 10 mA cm-2 current density) and low Tafel slope (82.1 mV deg-1). Again, this metal-free catalyst shows oxygen evolution reaction (OER) at 410 mV overpotential w.r.t RHE for 10 mA cm-2 current density with a lower Tafel slope of 104.5 mV deg-1. This bifunctional activity was further tested in two electrodes set-up under different pH conditions. The porosity seems to be a blessing in the electrocatalytic performance of this metal-free electrocatalyst material. Further, the mystery behind the activity of both HER and OER has been resolved through the density functional theory (DFT) analysis. This work provides an insight to the material scientists for low cost, metal-free material design for the efficient water splitting reaction.

Herein, we review notable points from observations of electrochemical reactions in a liquid electrolyte by liquid-phase electron microscopy. In situ microscopic observations of electrochemical reactions are urgently required, particularly to solve various battery issues. Battery performance is evaluated by various electrochemical measurements of bulk samples. However, it is necessary to understand the physical/chemical phenomena occurring in batteries to elucidate the reaction mechanisms. Thus, in situ microscopic observation is effective for understanding the reactions that occur in batteries. Herein, we focus on two methods, of the liquid phase (scanning) transmission electron microscopy and liquid phase scanning electron microscopy, and summarize the advantages and disadvantages of both methods.

The urgent issues related to the catalytic processes and energy applications have accelerated the development of hybrid and smart materials. MXenes are a new family of atomic layered nanostructured materials that require considerable research. Tailorable morphologies, strong electrical conductivity, great chemical stability, large surface-to-volume ratios, tunable structures, among others are some significant characteristics that make MXenes appropriate for various electrochemical reactions, including dry reforming of methane, hydrogen evolution reaction, methanol oxidation reaction, sulfur reduction reaction, Suzuki-Miyaura coupling reaction, water-gas shift reaction, and so forth. MXenes, on the other hand, have a fundamental drawback of agglomeration, as well as poor long-term recyclability and stability. One possibility for overcoming the restrictions is the fusion of nanosheets or nanoparticles with MXenes. Herein, the relevant literature on the synthesis, catalytic stability and reusability, and applications of several MXene-based nanocatalysts are deliberated including the merits and cons of the newer MXene-based catalysts.

Since the discovery of graphene, research on the family of 2D materials has been a thriving field. Metal phosphorous chalcogenides (MPX3 ) have attracted renewed attention due to their distinctive physical and chemical properties. The advantages of MPX3 , such as tunable layered structures, unique electronic properties, thermodynamically appropriate band alignments and abundant catalytic active sites on the surface, make MPX3 material great potential in electrocatalysis. In this review, the applications of MPX3 electrocatalysts in recent years, including hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction, are summarized. Structural regulation, chemical doping and multi-material composite that are often effective and practical research methods to further optimize the catalytic properties of these materials, are introduced. Finally, the challenges and opportunities for electrocatalytic applications of MPX3 materials are discussed. This report aims to advance future efforts to develop MPX3 and related materials for electrocatalysis.

Janus architectures have garnered great research efforts in recent years, leading to outstanding advances in electrocatalysis. Benefiting from the synergistic combination of their anisotropy which endows the manifestation of various co-existing electrochemical properties, and their compartmentalized structure that enables each functional domain to retain its inherent activity, with little to no interference from other domains, Janus architectures show great potential as exceptionally versatile electrocatalysts to complement a plethora of electrocatalytic processes. Thus, coupled with the growing interest in Janus architectures for electrocatalysis, it is imperative to investigate and reconsider their design strategies and future directions.

Electrocatalysis and electrosynthesis, which convert the electrical energy and store them in the chemical forms, have been considered as promising technologies to utilize green renewable energy sources. Most of the studies focused on developing novel active molecules or advanced electrodes to improve the performance. However, the direct acquisition and electron transferring will be limited by the intrinsic characters of the electrodes. The introduce of redox mediators, which are served as the intermediate electron carriers or reservoirs without changing the final products, provide a unique approach to accelerate the electrochemical performance of these energy conversions. This review provides an overview of the recent development of electrocatalysis and electrosynthesis by using redox mediators, and provides a comprehensive discussion toward focusing on the principles and construction of these systems.

Electrocatalytic hydrogen evolution reaction (HER) is critical for green hydrogen generation and exhibits distinct pH-dependent kinetics that have been elusive to understand. A molecular-level understanding of the electrochemical interfaces is essential for developing more efficient electrochemical processes. Here we exploit an exclusively surface-specific electrical transport spectroscopy (ETS) approach to probe the Pt-surface water protonation status and experimentally determine the surface hydronium pKa [Formula: see text] 4.3. Quantum mechanics (QM) and reactive dynamics using a reactive force field (ReaxFF) molecular dynamics (RMD) calculations confirm the enrichment of hydroniums (H3O[Formula: see text]) near Pt surface and predict a surface hydronium pKa of 2.5 to 4.4, corroborating the experimental results. Importantly, the observed Pt-surface hydronium pKa correlates well with the pH-dependent HER kinetics, with the protonated surface state at lower pH favoring fast Tafel kinetics with a Tafel slope of 30 mV per decade and the deprotonated surface state at higher pH following Volmer-step limited kinetics with a much higher Tafel slope of 120 mV per decade, offering a robust and precise interpretation of the pH-dependent HER kinetics. These insights may help design improved electrocatalysts for renewable energy conversion.

Visualization of the electrochemical reaction is essential for comprehensively understanding the electrochemical reaction mechanism and precisely characterizing dynamic electrochemical processes. Herein, we propose a simple device that combines light-addressable potentiometric sensor (LAPS) imaging and microelectrodes to serve as a general electroanalysis platform for the label-free sensing and imaging of electrochemical reactions. In this device, two microelectrodes are assembled on the LAPS chip. Electrochemical reactions occurring on the microelectrodes can be qualitatively and quantitatively observed and visualized using a LAPS chip that is sensitive to the reaction products. Validations were performed to monitor the effect of water electrolysis and potassium ferrocyanide oxidation surrounding the microelectrodes, respectively. We believe that this study will provide an excellent platform for the visualization and monitoring of electrochemical reactions and broaden the application scope of LAPS imaging to a general electroanalysis tool that is widely applicable in several fields.