Journal Articles

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12504/113

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Browsing Journal Articles by Author "Emma Panzi Mukhokosi"

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    Device architectures for photoelectrochemical water splitting based on hematite: a review
    (Discover Materials, 2024-08-21) Stella, Nasejje; Emma Panzi Mukhokosi; Mmantsae Diale; Dhayalan Velauthapilla
    Hydrogen production by photoelectrochemical (PEC) water splitting is a sustainable means that can avert the effects of global warming caused by fossil fuels. For decades, a suitable semiconductor that can absorb solar radiation in the visible region has been a focal research question. Hematite has a theoretical Solar-To-Hydrogen efficiency of 15% which is higher than the 10% benchmark for PEC water splitting. Despite being cheap, chemically stable, and bearing a desired band gap, hematite has not reached this projection due to challenges like band edge mismatch, short hole diffusion length and charge recombination. Various articles have shown hetero-structuring is a reliable solution to some challenges due to enhanced spectral range, enhanced carrier mobility, strong built-in electric field and thus increase in efficiency. However, these articles lack scientific rationale on the performance of hematite and its hetero-structures on different substrates, which is the basis for this review. Our analysis suggests that hetero-structure improves hematite’s PEC performance due to increased spectral range, enhanced carrier mobility and built-in electric field. This review article is organized as follows: a brief PEC background, performance parameters, Physical and Crystallographic properties of hematite, device configurations, performance of hematite and its hetero-structures on different substrates.
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    Temperature dependent microstructural defects and surface charge effects on antioxidant activity of green synthesized nanoceria
    (Scientific Reports, 2025-08-08) Musa Kabagambe; IsaAhuura; Sam Kinyera Obwoya; Emma Panzi Mukhokosi
    This study reports a novel eco-friendly route for synthesizing cerium dioxide nanoparticles (nanoceria) that converts waste coffee husks into both reagent and process medium. Polyphenol rich phytochemicals chelate Ce3+, guide hydrolysis, and locally modulate redox conditions, imprinting abundant surface Ce3+ and oxygen vacancies that underpin activity. Reuse of the clarified supernatant in successive cycles boosts yield exponentially without added metal oxide precursor, highlighting intrinsic process efficiency. Subsequent calcination turns the bio templated precipitate into phase pure fluorite CeO₂ whose crystallite size, strain, and defect concentration can be tuned by temperature alone. Higher temperatures enlarge particles and improve crystallinity while removing vacancies and strain. Radical scavenging assays show the highest activity in uncalcined material and a steady decline with increasing temperature that parallels the loss of surface Ce3+ and vacancies. Statistical analysis confirms that antioxidant performance depends on defect density, quantum confinement, and surface charge, whereas external morphology and residual organics are negligible. The unique mechanism is phytochemical-directed defect engineering, which couples the use of agricultural waste with precise control of redox-active sites to deliver tuneable nanoceria for biomedical, agricultural, and environmental remediation applications.