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<p>Metal-free nitrogen-doped carbons were prepared by D-glucose – citric acid polymerization followed by mild air carbonization. Structure and surface chemistry were examined by XRD and Raman for local graphitic order, XPS for nitrogen speciation, SEM-EDX for morphology and elemental distribution, and N<sub>2</sub> isothermal adsorption-desorption for textural properties. Catalytic tests for sodium borohydride methanolysis were carried out in anhydrous methanol at 30&#xa0;°C and 2.5 wt% NaBH<sub>4</sub>, with hydrogen volume logged in real time and initial rates used for Arrhenius analysis. The optimized catalyst, NC-CA2.0 reached an HGR of 5200 mL.g<sub>cat</sub><sup>−1</sup>.min⁻¹ at 30&#xa0;°C and showed an apparent activation energy of 25.4 ± 1.8&#xa0;kJ.mol⁻¹. Capacity was preserved over five cycles, whereas the peak rate declined to about 45% of the initial value. Together with strong inhibition by added base, the kinetic behavior is consistent with an interfacial Eley–Rideal pathway in which edge nitrogen assists adsorption or polarization of methanol and borohydride derived intermediates and N environments in more graphitized domains facilitate charge transport within the sp² framework. The data indicate that methanolysis performance is governed by the combination of local graphitic order and accessible edge nitrogen rather than by total nitrogen content, providing guidance for the design of robust metal-free carbons for on-demand hydrogen release.</p>

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Metal‑Free Nitrogen‑Doped Carbon Catalysts for NaBH4 Methanolysis: Spectroscopy‑Anchored Defect Descriptors for Low‑Temperature Hydrogen Release

  • 期刊论文

  • 发表日期：

    2026年2月2日

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  • Lam Nguyen-Dinh,
  • Cuong Pham-Huu,
  • Thanh Son Phan

摘要

Metal-free nitrogen-doped carbons were prepared by D-glucose – citric acid polymerization followed by mild air carbonization. Structure and surface chemistry were examined by XRD and Raman for local graphitic order, XPS for nitrogen speciation, SEM-EDX for morphology and elemental distribution, and N2 isothermal adsorption-desorption for textural properties. Catalytic tests for sodium borohydride methanolysis were carried out in anhydrous methanol at 30 °C and 2.5 wt% NaBH4, with hydrogen volume logged in real time and initial rates used for Arrhenius analysis. The optimized catalyst, NC-CA2.0 reached an HGR of 5200 mL.gcat−1.min⁻¹ at 30 °C and showed an apparent activation energy of 25.4 ± 1.8 kJ.mol⁻¹. Capacity was preserved over five cycles, whereas the peak rate declined to about 45% of the initial value. Together with strong inhibition by added base, the kinetic behavior is consistent with an interfacial Eley–Rideal pathway in which edge nitrogen assists adsorption or polarization of methanol and borohydride derived intermediates and N environments in more graphitized domains facilitate charge transport within the sp² framework. The data indicate that methanolysis performance is governed by the combination of local graphitic order and accessible edge nitrogen rather than by total nitrogen content, providing guidance for the design of robust metal-free carbons for on-demand hydrogen release.