n-Butanol/Water Interface-Aided Physicochemical Tuning of Two-Dimensional Transition-Metal Oxides

In Situ Generation of Porous Ag-Hollandite/Polypyrrole 2D Mats at the Water/Chloroform Interface for Dual Applications in Energy Storage and Electrochemical Sensing

A facile in situ method of the liquid/liquid (L/L) polymerization strategy for synthesizing silver-doped hollandite manganese oxide (Ag-HMO) on polypyrrole (PPy) support is reported for the first time. The highly innovative synthetic method involves producing α-MnO2 attached to PPy oligomers under low-temperature conditions. Subsequently, Ag+ ions are in situ intercalated into the 2 × 2 tunnels in α-MnO2 to generate Ag-HMO-incorporated PPy. Calculations based on density functional theory (DFT) yield negative formation energies, suggesting that Ag-HMO can be formed through the tunnel doping of Ag+ in α-MnO2. Highly crystalline 2D composite mats of Ag-HMO/PPy (PAgMn) with interconnected Ag-HMO nanorod networks with a thickness of ≈1 nm are demonstrated by electron and atomic force microscopy images. Electrochemical detection of formaldehyde on PAgMn-modified screen-printed electrodes opens new prospects for real-time food adulterant sensors. PAgMn is also utilized as electrodes for supercapacitors with a high specific capacitance of 601 mF cm-2. An all-solid-state asymmetric supercapacitor device assembled with PAgMn and activated carbon as negative and positive electrodes demonstrates outstanding energy storage capability with a remarkable energy density of 6.16 mWh cm-2 at a power density of 6300 mW cm-2.

Advances in Nickel-Based Catalysts for Alkaline Water Electrolysis: Comprehensive Review of Current Research Direction for HER and OER Applications

Nickel-based catalysts are among the most promising materials for electrocatalytic water splitting, particularly for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. Their abundance, cost-effectiveness, and tunable electrochemical properties make them attractive alternatives to precious metal catalysts. This review provides a comprehensive analysis of the advancements in nickel-based catalysts, including pure nickel, alloys, oxides, hydroxides, and spinels, emphasizing their synthesis methods, structural properties, and electrocatalytic performance. Recent nanostructuring, doping, and hybridization innovations with conductive supports have significantly enhanced catalytic activity, stability, and efficiency. Despite notable progress, challenges remain in improving long-term durability, minimizing surface degradation, and scaling up production for industrial applications. Addressing these limitations through advanced catalyst design, in situ characterization, and integration with renewable energy sources will be crucial for widely adopting nickel-based catalysts in sustainable hydrogen production. This review highlights the key developments and future directions in the field, underscoring the role of nickel-based materials in enabling the hydrogen economy and global decarbonization efforts.

Tailoring the Morphology of α-Cobalt Hydroxide Using Liquid/Liquid Interface and Its Application in Electrochemical Detection of Ascorbic Acid

The exertion of nanomaterials is subjugated by factors such as size, thickness, morphology, crystallinity, and composition, however, the ability to control these parameters, particularly the morphology, through conventional synthesis methods are challenging. Nevertheless, liquid/liquid interface-assisted methods have paved the way for more precise and controlled synthesis of nanomaterials. In this study, an n-butanol/water interface was used to synthesize α-cobalt hydroxide (CH) nanostructures, and the effects of solvent ratio and stirring rate on the properties of the product were examined. The transition from pure water to pure n-butanol alters the morphology from irregular nanoflakes to flower-like structures. A 1:1 solvent ratio produced nonaggregated flower structures with an increased active surface area and minimal charge transfer resistance. The agitation speed also affected the morphology; as the stirring speed increased from zero to 150 rpm, the morphology changed from aggregated needles to flower-like structures. The sample synthesized with a 1:1 solvent ratio and 50 rpm stirring speed (BW2) exhibited enhanced electrochemical activity, which was harnessed for electrochemical sensing with minimal multiwalled carbon nanotube (MWCNT) addition. The CH/MWCNT composite effectively detected ascorbic acid (AA) across a broad linear range of 1-200 μM with a detection limit of 0.0943 μM and provided accurate AA recovery in vitamin C tablets and artificial sweat. A flexible miniature sensor was also developed for AA detection, demonstrating the potential of liquid/liquid interfaces to modulate the morphology and hence the electrochemical properties of transition metal oxides for a wide range of applications.

Interfacial tension driven adsorption of MnO2 nanoparticles at the liquid/liquid interface to tailor ultra-thin polypyrrole sheets

An emerging aspect of research is designing and developing fully tunable metamaterials for various applications with fluid interfaces. Liquid/liquid interface-assisted methods represent an efficient and facile route for synthesizing two-dimensional (2-D) thin films of potential materials. The underlying mechanism behind thin film formation at the liquid/liquid interface involves the preferential adsorption of nano-sized particles at the interface to minimize high interfacial tension. Here, a water/chloroform interface-assisted method is employed for the one-pot synthesis of highly crystalline polypyrrole/manganese dioxide (PPy/MnO₂) sheets. The temporal evolution in the dynamic interfacial tension (from 32 mN m^-1 to 17 mN m^-1) observed in pendant drop tensiometry proved the preferential adsorption of MnO₂ atttached PPy oligomers at the water/chloroform interface. An ultra-thin sheet-like morphology and uniform distribution of ∼6 nm highly crystalline MnO₂ nanoparticles are evidenced by transmission and atomic force microscopy techniques. The predominance of interfacial polymerization in retaining the electrochemical activity of the PPy/MnO₂ sheets is elucidated for the electrochemical detection of nicotine. This study opens a new avenue for the realization of ultra-thin sheets of polymer-nanomaterial hybrids, enabling applications ranging from new classes of sensors to optics.

Interface-assisted synthesis: a gateway to effective nanostructure tuning of conducting polymers

The interface-assisted polymerization technique can be viewed as a powerful emerging tool for the synthesis of conducting polymers (CPs) on a large scale. Contrary to other bulk or single-phase polymerization techniques, interface-assisted synthesis strategies offer effective nanostructure control in a confined two-dimensional (2-D) space. This review focuses on the types of interfaces, mechanism at the interface, advantages and future perspectives of the interfacial polymerization in comparison to conventional polymerization techniques. Hence, the primary focus is on briefing the different types of the chemical methods of polymerization, followed by uniqueness in the reaction dynamics of interface polymerization. The classification of interfaces into four types (liquid/solid, gas/liquid, liquid/liquid, and gas/solid) is based on the versatility and underlying mechanistic pathway of the polymerization of each type. The role of interface in tuning the nanostructure of CPs and the performance evaluation of pristine CPs based on the electrical conductivity are also discussed. Finally, the future outlook of this emerging field is discussed and proposed in detail through some multifunctional applications of synthesized conducting polymers.

Soft-template-assisted synthesis: a promising approach for the fabrication of transition metal oxides

The past few decades have witnessed transition metal oxides (TMOs) as promising candidates for a plethora of applications in numerous fields. The exceptional properties retained by these materials have rendered them of paramount emphasis as functional materials. Thus, the controlled and scalable synthesis of transition metal oxides with desired properties has received enormous attention. Out of different top-down and bottom-up approaches, template-assisted synthesis predominates as an adept approach for the facile synthesis of transition metal oxides, owing to its phenomenal ability for morphological and physicochemical tuning. This review presents a comprehensive examination of the recent advances in the soft-template-assisted synthesis of TMOs, focusing on the morphological and physicochemical tuning aided by different soft-templates. The promising applications of TMOs are explained in detail, emphasizing those with excellent performances.