The removal of nitrogen species, particularly nitrates, is critically important for environmental remediation and the production of renewable energy. Converting nitrogen in wastewater into ammonia is an alternative to the Haber-Bosch process, which constitutes an effective and economical method for addressing nitrate contamination in source waters. This process simultaneously facilitates the reclamation of nitrogen as a renewable and promising energy resource. This approach not only decreases dependence on energy-consuming procedures but is also environmentally friendly. Copper-based electrocatalysts for the nitrogen/nitrate reduction reaction (NRR) have been widely studied, yet a comprehensive understanding of the relationships between their preparation, characterization, and catalytic activity remains incomplete. In this review, we aim to provide a structured summary of synthetic approaches for Cu-based electrodes using both physical and chemical methods, highlighting the structure–activity correlations between synthesis strategies and catalyst performance. We also present a thorough overview of advanced characterization techniques, including structural, morphological, compositional, electrochemical, and in situ/operando studies, to identify active sites, reaction intermediates, and degradation pathways. The electrocatalytic performance of Cu-based electrodes in NRR is critically analyzed and compared, with emphasis on the effects of morphology, surface composition, electrolyte selection, and pH on activity and selectivity. Methods for quantifying ammonia, such as colorimetry, NMR, GC, and ion chromatography, are reviewed to ensure benchmarking and reproducibility. Despite these advances, practical application remains limited due to challenges such as the trade-off between selectivity and activity, catalytic deactivation, and competition from the hydrogen evolution reaction (HER). This work aims to provide a consistent and rational framework for screening Cu-based systems toward highly efficient and cost-effective ammonia electrosynthesis.
Graphene quantum dots (GQDs) derived from nanocellulose were prepared with and without sulfuric acid pre-treatment, and applied in dye-sensitized solar cells (DSSCs). Using nanocellulose, a renewable carbon precursor from wood pulp, supports the development of bio-based materials for bioenergy and solar-to-electric energy conversion. Although acid treatment enhanced −COOH functionalization, excessive oxidation introduced structural defects that increased charge recombination and reduced photovoltaic performance. Acid-free GQDs produced higher photocurrent density than acid-treated samples, indicating better structural preservation and charge transport. However, both systems underperformed relative to conventional N719-only cells due to limited visible-light absorption and energy-level misalignment. Overall, acid-free synthesis offers a more sustainable route to nanocellulose-derived GQDs for environmentally friendly bioenergy and solar cell applications.
Heat transfer is frequently employed in various industrial processes such as paper production, electronic device cooling, and the synthesis of new materials. Hence, this study aims to investigate the effect of Joule heating and magnetohydrodynamics (MHD) on the flow of a hybrid nanofluid with a power law heat flux past a shrinking sheet. The transformed governing equations are solved numerically using MATLAB’s bvp4c solver, and the results are validated against previously published data, showing excellent agreement (error < 0.01
Reliable dimensional inspection with handheld 3D scanners is frequently affected by unstable environmental conditions, reflective surfaces, and operator-dependent variability. This study introduces a practical, industry-oriented workflow designed to minimize noise during both acquisition and post-processing. The approach combines controlled lighting and temperature management, surface preparation using matte spray coatings, and optimized scanning trajectories to enhance data capture stability. These acquisition strategies are followed by a structured post-processing pipeline in Artec Studio 17, emphasizing targeted noise filtering while preserving small geometric features. Three machined components of differing complexity were evaluated, with dimensional accuracy assessed against their corresponding CAD models. The proposed workflow yielded average improvements of 1–2
We report the first demonstration of a Zn (II) Schiff base complex deposited onto a side-polished fiber (SPF) as a saturable absorber (SA) for soliton mode-locking in an erbium-doped fiber laser (EDFL). The complex was synthesized via a one-pot reflux condensation of 1,2-phenylenediamine and 2,4-dihydroxybenzaldehyde, followed by coordination with zinc (II) acetate, and subsequently dissolved in dimethyl sulfoxide solution. The mixed solution was drop-cast onto the SPF to harness the strong evanescent field interaction, forming an integrated all-fiber SA device. Incorporation of the device into a ring-cavity EDFL enabled stable soliton pulse generation at 1569.03 nm, delivering 1.30 ps pulses at a repetition rate of 1.91 MHz. The laser exhibited a linear increase in output power, pulse energy, and peak power with pump power. At a pump power of 138.68 mW, the pulse energy and peak power reached 1.96 nJ and 1.51 kW, respectively. These results demonstrate that the Zn (II)-complex-coated SPF serves as a novel, practical, and efficient SA for compact and power-scalable ultrafast fiber lasers.
