Kamal Prasad Sapkota

Trapping active metal oxides within noncrystalline carbon tubes (nCTs) offers unique advantages for electrocatalysis, including abundant dangling bonds, a high surface-to-volume ratio, excellent conductivity, and enhanced long-term durability. However, precise control of the oxide phase during heat treatment remains a key challenge. Herein, we systematically investigate the phase composition of copper oxides (Cu_xO, x = 0,1,2) confined within nCTs, depending on temperature and ramp rate, and explore their application in electrochemical alkaline water splitting. Comprehensive spectroscopic and microscopic analyses reveal that both parameters critically influence the structural and compositional integrity of the composites. Among the synthesized materials, the optimized electrode, nCT-Cu₂O/CuO, delivers superior electrocatalytic performance, achieving a current density of 10 mA/cm² at relatively low overpotentials of 168 mV for the hydrogen evolution reaction (HER) and 284 mV for the oxygen evolution reaction (OER). Favorable Tafel slopes of 73 for HER and 62 mV/dec for OER further underscore its excellent kinetics. The electrolyzer based on the as-synthesized electrodes delivers a current density of 10 mA/cm² at a cell potential as low as 1.57 V. Experimental observations, supported by density functional theory calculations for both HER and OER, attribute these outstanding properties to the combined effects of the well-dispersed CCO nanoparticles within the nCT matrix, which enhance active site density, promote charge transfer, and introduce confinement effects. This work presents a cost-effective and scalable strategy for fabricating efficient bifunctional electrodes, offering insights for advancing sustainable hydrogen production technologies.

The present research work reports the successful synthesis of the iron oxide nanoparticles (IONPs) through green route, their characterization and their application for their antimicrobial and photocatalytic performance. The IONPs were prepared using Citrus maxima peel extract through green synthesis method. The peel extract was found to contain important phytochemicals such as polyphenols, flavonoids, and terpenoids, which facilitate the reduction of metal precursors and stabilize metal nanoparticles. This approach offers scalability, simplicity, and non-toxicity, making it a notable strategy in green nanotechnology for producing nanoparticles. The as-synthesized nanoparticles were applied for the antimicrobial and photocatalytic performance. It was found that the as-synthesized IONPs were excellent photocatalysts for the degradation of methylene blue solution with 98.13% degradation within the recorded time of 90 minutes in the presence of natural sunlight. Moreover, the IONPs demonstrated good anti-bacterial activity against Bacillus subtilis and E. coli and good anti-fungal activity against Candida albicans.

We present the fabrication and proficient photocatalytic performance of a series of heterojunction nanocomposites with cauliflower-like architecture synthesized from copper(II) oxide (CuO) nanocrystals and carbon nanotubes with single walls (SWCNTs). These unique photocatalysts were constructed via simplistic recrystallization succeeded by calcination and were labeled as CuOSC-1, CuOSC-2, and CuOSC-3 (representing the components; CuO and SC for SWCNTs, and the calcination time in hours). The photocatalytic potency of the fabricated nanocomposites was investigated on the basis of their capability to decompose methylene blue (MB) dye under visible-light irradiation. Every as-synthesized nanocomposite was effective photocatalyst for the photodecomposition of an MB solution. Moreover, CuOSC-3 exhibited the best photocatalytic activity, with 96% degradation of the visible-light irradiated MB solution in 2 h. Pure CuO nanocrystals generated through the same route and pure SWCNTs were used as controls, where the photocatalytic actions of the nanocomposite samples were found to be remarkably better than that of either the pure CuO or the pure SWCNTs. The recycling proficiency of the photocatalysts was also explored; the results disclosed that the samples could be applied for five cycles without exhibiting a notable change in photocatalytic performance or morphology.

We report enhanced catalytic action of a series of copper(II)-oxide-single-walled carbon nanotube (CuO-SWCNT) composite photocatalysts (abbreviated as CuO-SWCNT-0.5, CuO-SWCNT-2, and CuO-SWCNT-5, where 0.5, 2, and 5 represent the calcination time in hours) synthesized via recrystallization followed by calcination. The photocatalytic performance of the fabricated nanocomposites was examined by evaluating the degradation of methylene blue (MB) under irradiation with visible light. All of the as-fabricated nanocomposites were effective photocatalysts for the photodegradation of a MB solution; however, the CuO-SWCNT-5 displayed the best photocatalytic ability among the investigated catalysts, achieving 97.33% degradation of MB in 2 h under visible-light irradiation. The photocatalytic action of the nanocomposites was remarkably higher than that of pristine CuO nanocrystals fabricated using the same route. The recyclability of the photocatalyst was also investigated; the CuO-SWCNT-5 catalyst could be reused for three cycles without substantial degradation of its catalytic performance or morphology.

ZnO nanoparticles (ZnO-NPs) were synthesized by a straightforward modified thermal method using only one chemical: zinc acetate dihydrate. The process is environmentally safer than other methods because it does not involve other chemicals or a catalyst, acid, or base source. X-ray diffraction analysis indicated that the ZnO-NPs crystallize in the hexagonal wurtzite structure. The UV–vis absorption spectra revealed a marked redshift, which is critical for enhanced photocatalytic activity. We used methylene blue for photocatalytic activity tests and found an excellent degradation percentage (99.7%) within a short time (80 min). The antibacterial activity of the synthesized ZnO-NPs was tested against Escherichia coli at different concentrations of ZnO-NPs. The analysis revealed that the minimum inhibitory concentration (MIC) of the ZnO-NPs against E. coli was 30–50 μg/mL. Our ZnO-NPs were found to be more effective than previously reported ZnO-NPs synthesized via other methods.