Mélanie Emo

Luffa peel extract was employed to investigate its impact on the morphology, particle size, surface properties, optical band gap, and surface active sites of nickel oxide (NiO). Various analytical techniques revealed that the synthesized NiO nanostructures, prepared using 2 mL of luffa peel extract, exhibited a distinctive flower-like morphology, the smallest particle size, abundant surface oxygen vacancies, the narrowest optical band gap, and enhanced surface catalytic activity. The electrochemical non-enzymatic method demonstrated significant efficiency in oxidizing uric acid (UA) in phosphate buffer solution at pH 7.3, utilizing sample 3 of the NiO nanostructures. Sample 3 exhibited a broad linear detection range for UA, spanning from 0.1 to 15 mM, along with an exceptionally low limit of detection of 0.004 mM, as determined through chronoamperometry. Furthermore, sample 3 of NiO was found to be highly stable, reproducible, and selective. Non-enzymatic UA sensors were successfully applied to quantify UA levels in blood and urine samples, yielding highly accurate results with a relative standard deviation of less than 3%. This research highlights the potential of luffa peel extract in the development of a diverse range of electrocatalytic materials for applications in clinical diagnostics, biomedical research, and related fields.

Encapsulating Fe₃C in carbon layers has emerged as an innovative strategy for protecting Fe₃C while preserving its high oxygen reduction activity. However, fundamental questions persist regarding the active sites of encapsulated Fe₃C due to the restricted accessibility of oxygen molecules to the metal sites. Herein, the intrinsic electron transfer mechanisms of Fe₃C nanoparticles encapsulated in N‐doped carbon materials are unveiled for oxygen reduction electrocatalysis. The precision‐structured C₁N₁ material is used to synthesize N‐doped carbons with encapsulated Fe₃C, significantly enhancing catalytic activity (E_ONSET = 0.98 V) and achieving near‐100% operational stability. In anion‐exchange membrane fuel cells, an excellent peak power density of 830 mW cm⁻² is reached at 60 °C. The experimental and computational results revealed that the presence of Fe₃C cores dynamically triggers electron transfer to the outermost carbon layer. This phenomenon amplifies the oxygen reduction reaction performance at N sites, contributing significantly to the observed catalytic enhancement.

Single atoms and nanoclusters of Fe, Ni, Co, Cu, and Mn are systematically designed and embedded in a well‐defined C₁N₁‐type material that has internal cavities of ≈0.6 nm based on four N atoms. These N atoms serve as perfect anchoring points for the nucleation of small nanoclusters of different metal natures through the creation of metal‐nitrogen (TM‐N₄) bonds. After pyrolysis at 800 °C, TM@CN_x‐type structures are obtained, where TM is the transition metal and x < 1. Fe@CN_x and Co@CN_x are the most promising for oxygen reduction reaction and hydrogen evolution reaction, respectively, with a Pt‐like performance, and Ni@CN_x is the most active for oxygen evolution reaction (OER) with an E_OER of 1.59 V versus RHE, far outperforming the commercial IrO₂ (E_OER = 1.72 V). This systematic and benchmarking study can serve as a basis for the future design of advanced multi‐functional electrocatalysts by modulating and combining the metallic nature of nanoclusters and single atoms.