NH3 decomposition activity of Ru supported on hydrothermally derived carbon: Temperature effectson the morphological evolution

IF 4.8 2区化学 Q2 CHEMISTRY, PHYSICAL

Applied Catalysis A: General Pub Date : 2025-10-01 DOI:10.1016/j.apcata.2025.120616

Miranda Guci , Markus Knäbbeler-Buß , Emma Verkama , Michael Günthel , Md Redwanul Islam , Lorenz Kienle , Erisa Saraçi , Jan-Dierk Grunwaldt , Florian Nestler

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引用次数: 0

Abstract

A hydrothermally derived carbon support was synthesized from the sustainable feedstock chitosan, with optional subsequent pyrolysis at 600 °C and 1000 °C, to explore its potential as a catalyst support material for ruthenium (Ru). The catalysts were prepared through wet impregnation using Ru nitrosyl nitrate as the precursor. Their catalytic performances in ammonia decomposition were investigated under conditions of 5 % NH₃ at 1 bar, within a temperature range of 300 °C to 600 °C, and a weight hourly space velocity of 15.000 ml_N g_cat⁻¹ h⁻¹. The analytical techniques employed in this study included elemental analysis, thermogravimetric analysis (TGA), gas adsorption measurements, Raman spectroscopy, X-ray diffraction (XRD), flame atomic absorption spectroscopy (F-AAS), scanning transmission electron microscopy (STEM), hydrogen-based temperature-programmed reduction (H₂-TPR) and X-ray photoelectron spectroscopy (XPS). They unraveled that non-pyrolyzed supports showed a strong tendency for Ru agglomeration, whereas pyrolyzed supports exhibited improved metal distribution, which correlated with enhanced catalytic activity exceeding 50 % ammonia conversion at 450 °C. The surface chemistry of the carbon support was modified by varying the pyrolysis temperature, which affected the concentrations and types of oxygen and nitrogen surface groups. These changes altered the interaction between Ru and these surface groups. During the decomposition of the Ru precursor and the reduction of Ru oxides, the partial breakdown of oxygen and nitrogen surface groups led to surface reconstructions of the Ru nanoparticles, thereby affecting their crystallinity. This phenomenon was also observed during the catalytic testing, which was more pronounced on the HC-600 support. Modifying the surface chemistry of hydrochar via pyrolysis affects Ru distribution, reducibility, and crystallinity, thereby enhancing the NH₃ decomposition performance.

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水热衍生碳负载Ru的NH3分解活性：形态演化中的温度效应

以壳聚糖为原料制备了水热衍生碳载体，并在600°C和1000°C下进行了选择性热解，以探索其作为钌（Ru）催化剂载体的潜力。以硝酸亚硝基钌为前驱体，采用湿浸渍法制备催化剂。在5 % NH₃、1 bar、300℃~ 600℃、重量/小时空速15.000 mlN gcat−1 h−1的条件下，研究了它们在氨分解中的催化性能。本研究采用的分析技术包括元素分析、热重分析（TGA）、气体吸附测量、拉曼光谱、x射线衍射（XRD）、火焰原子吸收光谱（F-AAS）、扫描透射电子显微镜（STEM）、氢基程序升温还原（H2-TPR）和x射线光电子能谱（XPS）。他们发现，未热解的载体表现出强烈的Ru团聚倾向，而热解的载体表现出更好的金属分布，这与450°C下超过50% %氨转化率的催化活性增强相关。热解温度的变化改变了碳载体的表面化学性质，影响了氧和氮表面基团的浓度和类型。这些变化改变了钌与这些表面基团之间的相互作用。在Ru前驱体分解和Ru氧化物还原过程中，氧和氮表面基团的部分击穿导致Ru纳米颗粒的表面重构，从而影响其结晶度。在催化试验中也观察到这种现象，在HC-600载体上更为明显。通过热解改性烃类的表面化学性质，可以影响Ru的分布、还原性和结晶度，从而提高NH₃的分解性能。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Applied Catalysis A: General 化学-环境科学

CiteScore

9.00

自引率

5.50%

发文量

415

审稿时长

24 days

期刊介绍： Applied Catalysis A: General publishes original papers on all aspects of catalysis of basic and practical interest to chemical scientists in both industrial and academic fields, with an emphasis onnew understanding of catalysts and catalytic reactions, new catalytic materials, new techniques, and new processes, especially those that have potential practical implications. Papers that report results of a thorough study or optimization of systems or processes that are well understood, widely studied, or minor variations of known ones are discouraged. Authors should include statements in a separate section "Justification for Publication" of how the manuscript fits the scope of the journal in the cover letter to the editors. Submissions without such justification will be rejected without review.