K2Ti6O13 Nanoparticle-Loaded Porous rGO Crumples for Supercapacitors

Ti3C2Tx MXene-supported ruthenium nanoclusters for efficient electrocatalytic hydrogen evolution

Developing an efficient and stable catalyst is both attractive and challenging for the electrochemical hydrogen evolution reaction (HER) due to the aggravation under the operating environment. MXene (Ti3C2Tx) is a potential catalyst support because of its abundant surface functional groups and unique hydrophilicity. However, anchoring noble metals onto MXene to construct high-performance electrocatalysts still presents some challenges. Herein, we present an MXene nanoparticle-supported Ru nanocluster (Ru@MXene-NP) electrocatalyst for HER. The Ru@MXene-NP not only effectively prohibits self-stacking but also ensures the full exposure of Ru nanoclusters. Thus, the Ru@MXene-NP catalyst exhibits an overpotential of 38.4 mV at 10 mA cm-2 and a Tafel slope of 26.4 mV dec-1 in an acidic medium, showcasing superior performance compared to most previously reported MXene-based catalysts. The small Tafel slope and low charge transfer resistance (Rct = 0.39 Ω) value indicate its fast electron transfer behavior. In addition, cyclic voltammetry curves and chronoamperometry tests demonstrate the high stability of Ru@MXene-NP. This work offers a novel perspective for designing catalysts by supporting noble metal nanoclusters on the MXene substrate's surface.

Investigating composite electrode materials of metal oxides for advanced energy storage applications

Electrochemical energy systems mark a pivotal advancement in the energy sector, delivering substantial improvements over conventional systems. Yet, a major challenge remains the deficiency in storage technology to effectively retain the energy produced. Amongst these are batteries and supercapacitors, renowned for their versatility and efficiency, which depend heavily on the quality of their electrode materials. Metal oxide composites, in particular, have emerged as highly promising due to the synergistic effects that significantly enhance their functionality and efficiency beyond individual components. This review explores the application of metal oxide composites in the electrodes of batteries and SCs, focusing on various material perspectives and synthesis methodologies, including exfoliation and hydrothermal/solvothermal processes. It also examines how these methods influence device performance. Furthermore, the review confronts the challenges and charts future directions for metal oxide composite-based energy storage systems, critically evaluating aspects such as scalability of synthesis, cost-effectiveness, environmental sustainability, and integration with advanced nanomaterials and electrolytes. These factors are crucial for advancing next-generation energy storage technologies, striving to enhance performance while upholding sustainability and economic viability.

Electrochemical and electrical characteristics of ball milled Cs2Ti6O13 modified by the surface-to-bulk migration of hydroxyl groups

Ball milling of solids under benign conditions leads to surface functionalization without altering the crystal structure and morphology. However, these additional surface functional groups are rarely fixed but instead mobilized across such ball milled solids. This phenomenon, including its effects on electrochemical and electrical properties, has received limited attention. We report herein that dry vibratory ball milling of lepidocrocite-type Cs2Ti6O13 generated hydroxyl groups which subsequently migrated from surfaces to bulk. The increased number of bulk hydroxyl groups is deduced from Raman, IR, and solid state 1H nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. In contrast, the decrease in the relative proportion of surface hydroxyl groups/water and carbon-oxygen species was deduced from X-ray photoelectron spectroscopy. The inaccessible hydroxyl groups in ball milled Cs2Ti6O13 lead to a smaller amount of stored charge and increased charge transfer resistance, according to galvanostatic charge-discharge experiments and electrochemical impedance spectroscopy studies in 1 M Na2SO4. The alternating current electrical properties were also measured, revealing fundamental insights such as the one-dimensional conduction pathway and the relaxation time in microseconds. A model has been proposed for this surface-to-bulk migration of the hydroxyl groups, which competes with surface dangling bonds leading to particle agglomeration.

Ni-citric acid coordination polymer as a practical catalyst for multicomponent reactions

Coordinative polymers (CP) are a subclass of Metal-organic frameworks (MOFs) with porous microstructures which have been widely synthesized in recent years and applied in various fields especially in catalysis science. In this work Coordinative polymers (CP) of nickel and citric acid (CA) was prepared as a new catalyst (Ni-CP) and applied in organic multicomponent reactions. The obtained catalyst was characterized by SEM, WDX, EDS, AAS, FT-IR, XRD and BET analysis. N2 adsorption-desorption isotherms indicate good BET surface area for Ni-CP; therefore can be employed as an efficient catalyst in multicomponent reactions for the synthesis of polyhydroquinoline and 2,3-dihydroquinazolin-4(1H)-one derivatives. Finally, this catalyst was recovered and reused several consecutive times.