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Upcycling Bio and Battery Waste Into Multivalent Calcium–Manganese Oxide Nanocomposites
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DOI：10.1002/cmtd.70149.png)
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Abstract
En 中文
Transforming chemically complex waste streams into high-performance calcium–manganese oxide multivalent nanocomposites (MNC) provides a promising route toward circular and sustainable materials engineering. Here, we report the synthesis of compositionally tunable Ca–Mn MNC derived entirely from waste eggshells and spent alkaline batteries through hydrothermal processing. In situ X-ray diffraction (XRD) revealed strongly composition-dependent thermal phase evolution, with Ca:Mn = 25:75 sample stabilizing mixed-valence Mn oxide phases with cubic CaMn7O12 quadruple perovskite phases while Ca:Mn = 75:25 sample was dominated by highly crystalline CaO phases. STEM-EELS and XPS analyses demonstrated substantial heterogeneity of Mn valence between the 25CaMn and 50CaMn catalysts, confirming the coexistence of Mn2+, Mn3+, and Mn4+-type environments through spatial variation in the Mn L3/L2 ratio associated with 3d electronic transitions. Among the investigated compositions, 25CaMn exhibited a CO2 space–time yield (STY) of 57 mmolCO2.g−1cat.h−1 57 mmolCO2.gcat−1.h−1$$ {\text{57 mmol}}_{{\mathrm{CO}}_{2}}.{\mathrm{g}}_{\text{cat}}^{-1}.{\mathrm{h}}^{-1}$$ and achieved ∼85% CO conversion near 300 °C, whereas 50CaMn delivered the highest overall CO2 productivity with a maximum STY of 60 mmolCO2.g−1cat.h−1 60 mmolCO2.gcat−1.h−1$$ {\text{60 mmol}}_{{\mathrm{CO}}_{2}}.{\mathrm{g}}_{\text{cat}}^{-1}.{\mathrm{h}}^{-1}$$ between 350 and 400 °C. Excessive Ca incorporation in 75CaMn suppressed Mn lattice participation and lowered catalytic activity at intermediate temperatures. This work demonstrates how waste-derived precursor engineering can generate multivalent electronic structure and catalytic functionality.
Keywords:
bio-waste
CO oxidation
e-waste
in situ XRD
STEM-EELS
upcycling
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