Electrochemical Oxidation of Urea on NiCu Alloy Nanoparticles Decorated Carbon Nanofibers

Unraveling the Oxidation Kinetics Through Electronic Structure Regulation of MnCo2O4.5@Ni3S2 p-n Junction for Urea-Assisted Electrocatalytic Activity

A promising strategy to boost electrocatalytic performance is via assembly of hetero-nanostructured electrocatalysts that delivers the essential specific surface area and also active sites by lowering the reaction barrier. However, the challenges associated with the intricate designs and mechanisms remain underexplored. Therefore, the present study constructs a p-n junction in a free-standing MnCo2O4.5@Ni3S2 on Ni-Foam. The space-charge region's electrical characteristics is dramatically altered by the formed p-n junction, which enhances the electron transfer process for urea-assisted electrocatalytic water splitting (UOR). The optimal MnCo2O4.5@Ni3S2 electrocatalyst results in greater oxygen evolution reactivity (OER) than pure systems, delivering an overpotential of only 240 mV. Remarkably, upon employing as UOR electrode the required potential decreases to 30 mV. The impressive performance of the designed catalyst is attributed to the enhanced electrical conductivity, greater number of electrochemical active sites, and improved redox activity due to the junction interface formed between p-MnCo2O4.5 and n-Ni3S2. There are strong indications that the in situ formed extreme-surface NiOOH, starting from Ni3S2, boosts the electrocatalytic activity, i.e., the electrochemical  surface reconstruction generates the active species. In conclusion, this work presents a high-performance p-n junction design for broad use, together with a viable and affordable UOR electrocatalyst.

Green structure orienting and reducing agents of wheat peel extract induced abundant surface oxygen vacancies and transformed the nanoflake morphology of NiO into a plate-like shape with enhanced non-enzymatic urea sensing application

Researchers are increasingly focusing on using biomass waste for green synthesis of nanostructured materials since green reducing, capping, stabilizing and orientation agents play a significant role in final application. Wheat peel extract contains a rich source of reducing and structure orienting agents that are not utilized for morphological transformation of NiO nanostructures. Our study focuses on the role of wheat peel extract in morphological transformation during the synthesis of NiO nanostructures as well as in non-enzymatic electrochemical urea sensing. It was observed that the morphological transformation of NiO flakes into nanoplatelets took place in the presence of wheat peel extract during the preparation of NiO nanostructures and that both the lateral size and thickness of the nanostructures were significantly reduced. Wheat peel extract was also found to reduce the optical band gap of NiO. A NiO nanostructure prepared with 5 mL of wheat peel extract (sample 2) was highly efficient for the detection of urea without the use of urease enzyme. It has been demonstrated that the induced modification of NiO nanoplatelets through the use of structure-orienting agents in the wheat peel has enhanced their electrochemical performance. A linear range of 0.1 mM to 13 mM was achieved with a detection limit of 0.003 mM in the proposed urea sensor. The performance of the presented non-enzymatic urea sensor was evaluated in terms of selectivity, stability, reproducibility, and practical application, and the results were highly satisfactory. As a result of the high surface active sites on sample 2, the low charge transfer resistance, as well as the high exposure to the surface active sites of wheat peel extract, sample 2 demonstrated enhanced performance. The wheat peel extract could be used for the green synthesis of a wide range of nanostructured materials, particularly metal/metal oxides for various electrochemical applications.

Coordination Polymer Framework-Derived Ni-N-Doped Carbon Nanotubes for Electro-Oxidation of Urea

Electrochemical oxidation of urea (UOR) is critical in the removal of urea from wastewater and energy conservation and storage. Nickel-based catalysts are widely used for urea-ORR, but in all cases, the nickel must be hybridized with carbon materials to improve its conductivity. In this manuscript, we demonstrate the synthesis of a nickel-decorated carbon nanotube (Ni-NCNT) by simple microwave pyrolysis of Dabco (1,4-diazabicyclo[2.2.2]octane)-based coordination polymer frameworks (CPF). The surface structure, morphology and chemical composition of Ni-NCNT were characterized by Raman spectrum, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy (EDS) analysis. SEM studies showed micrometer-long bamboo-shaped CNTs with nickel nanoparticles anchored to the walls and inside the nanotubes. A structural study by TEM and Raman spectra showed that carbon nanotubes are rich in defects due to the presence of nitrogen, and this was confirmed by energy-dispersive X-ray spectroscopy (EDS) maps. When applied as electrocatalysts in urea oxidation reactions (UOR), our newly developed Ni-NCNT shows excellent electrocatalytic activity and stability, making it a versatile catalyst in energy generation and mitigating water contamination.

Catalytic and Photocatalytic Electrospun Nanofibers for Hydrogen Generation from Ammonia Borane Complex: A Review

Hydrogen (H₂) is a promising renewable energy source that can replace fossil fuels since it can solve several environmental and economic issues. However, the widespread usage of H₂ is constrained by its storage and safety issues. Many researchers consider solid materials with an excellent capacity for H₂ storage and generation as the solution for most H₂-related issues. Among solid materials, ammonia borane (abbreviated hereafter as AB) is considered one of the best hydrogen storage materials due to its extraordinary H₂ content and small density. However, the process must be conducted in the presence of efficient catalysts to obtain a reasonable amount of generated H₂. Electrospun nanofibrous catalysts are a new class of efficient catalysts that involves the usage of polymers. Here, a comprehensive review of the ceramic-supported electrospun NF catalysts for AB hydrolysis is presented, with a special focus on catalytic and photolytic performance and preparation steps. Photocatalytic AB hydrolysis was discussed in detail due to its importance and promising results. AB photocatalytic hydrolysis mechanisms under light were also explained. Electrospun catalysts show excellent activity for AB hydrolysis with good recyclability. Kinetics studies show that the AB hydrolysis reaction is independent of AB concentration and the first-order reaction of NF catalysts.

Polarized Catalytic Polymer Nanofibers

Molecular scale modifications were achieved by spontaneous polarization which is favored in enhancements of β-crystallization phase inside polyvinylidene fluoride (PVDF) nanofibers (NFs). These improvements were much more effective in nano and submicron fibers compared to fibers with relatively larger diameters. Metallic nanoparticles (NPs) supported by nanofibrous membranes opened new vistas in filtration, catalysis, and serving as most reliable resources in numerous other industrial applications. In this research, hydrogenation of phenol was studied as a model to test the effectiveness of polarized PVDF nanofiber support embedded with agglomerated palladium (Pd) metallic nanoparticle diameters ranging from 5–50 nm supported on polymeric PVDF NFs with ~200 nm in cross-sectional diameters. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Energy Dispersive X-Ray Spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR) and other analytical analysis revealed both molecular and surface morphological changes associated with polarization treatment. The results showed that the fibers mats heated to their curie temperature (150 °C) increased the catalytic activity and decreased the selectivity by yielding substantial amounts of undesired product (cyclohexanol) alongside with the desired product (cyclohexanone). Over 95% phenol conversion with excellent cyclohexanone selectivity was obtained less than nine hours of reaction using the polarized PVDF nanofibers as catalytic support structures.