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<p>Catalytic decomposition of methane (CDM) enables CO<sub>x</sub>-free H<sub>2</sub> while co-producing solid carbon. Its viability hinges on catalysts that couple high activity with stable carbon co‑product formation. We evaluate Ni catalysts on FeAl<sub>2</sub>O<sub>4</sub> (hercynite) and identify ~ 40 wt% NiO as the optimum loading that balances activity with carbon yield. Promoter screening (La, Mg, Co; 5 wt%) reveals distinct control of reducibility and metal–support interaction (MSI). La lowers the reduction temperature, refines Ni/NiO crystallites, and increases Ni dispersion, delivering the highest initial CH<sub>4</sub> conversion (52.3%) and H<sub>2</sub> production rate (90.6 mmol g<sub>cat</sub><sup>−1</sup> min<sup>−1</sup>), albeit with deactivation at ~ 150&#xa0;min due to rapid carbon encapsulation. Mg strengthens the MSI and stabilizes residual NiO through MgO/MgAl<sub>2</sub>O<sub>4</sub>, lowering the initial activity. In contrast, Co promotes spinel formation and Ni aggregation, yielding the weakest activity. CDM is highly selective to H<sub>2</sub> with carbon as the sole co-product; the carbon forms multi-walled carbon nanotubes (MWCNTs) with ~ 16–24&#xa0;nm diameters. Operating parameters further tune performance, with 650&#xa0;°C being most effective. Lowering the space velocity extends the time-on-stream to ~ 450&#xa0;min, increases the initial conversion to 59.4%, and raises the carbon yield from ~ 970% to ~ 1470%. Comprehensive characterization links promoter-dependent reducibility and metal–support interaction to activity, stability, and MWCNT yield. These results provide practical guidance for co-optimizing composition and operating conditions in CDM. NiO/FeAl<sub>2</sub>O<sub>4</sub> with ~ 40 wt% NiO can serve as a baseline; La addition elevates initial rates, and operating at lower space velocity mitigates carbon-induced deactivation, thereby increasing H<sub>2</sub> productivity and improving CNT quality.</p>

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Promoter-Driven enhancement of NiO/FeAl2O4 catalysts for efficient carbon nanotube synthesis and COx-Free hydrogen production via methane pyrolysis

  • 期刊论文

  • 发表日期：

    2026年1月26日

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  • Shaikh Shayan Siddiqui,
  • Nodira Urol Kizi Saidova,
  • Soo Hong Lee,
  • Ji Sun Im

摘要

Catalytic decomposition of methane (CDM) enables COx-free H2 while co-producing solid carbon. Its viability hinges on catalysts that couple high activity with stable carbon co‑product formation. We evaluate Ni catalysts on FeAl2O4 (hercynite) and identify ~ 40 wt% NiO as the optimum loading that balances activity with carbon yield. Promoter screening (La, Mg, Co; 5 wt%) reveals distinct control of reducibility and metal–support interaction (MSI). La lowers the reduction temperature, refines Ni/NiO crystallites, and increases Ni dispersion, delivering the highest initial CH4 conversion (52.3%) and H2 production rate (90.6 mmol gcat−1 min−1), albeit with deactivation at ~ 150 min due to rapid carbon encapsulation. Mg strengthens the MSI and stabilizes residual NiO through MgO/MgAl2O4, lowering the initial activity. In contrast, Co promotes spinel formation and Ni aggregation, yielding the weakest activity. CDM is highly selective to H2 with carbon as the sole co-product; the carbon forms multi-walled carbon nanotubes (MWCNTs) with ~ 16–24 nm diameters. Operating parameters further tune performance, with 650 °C being most effective. Lowering the space velocity extends the time-on-stream to ~ 450 min, increases the initial conversion to 59.4%, and raises the carbon yield from ~ 970% to ~ 1470%. Comprehensive characterization links promoter-dependent reducibility and metal–support interaction to activity, stability, and MWCNT yield. These results provide practical guidance for co-optimizing composition and operating conditions in CDM. NiO/FeAl2O4 with ~ 40 wt% NiO can serve as a baseline; La addition elevates initial rates, and operating at lower space velocity mitigates carbon-induced deactivation, thereby increasing H2 productivity and improving CNT quality.