In this study, ultrasmall Ni nanoparticles (Ni NPs) were controllably supported in the cage-type mesopores of −COOH-functionalized mesoporous silica SBA-16 (denoted as Ni(x)@S16C, where x is the Ni loading) via wet impregnation under alkaline conditions, followed by thermal reduction. The particle sizes of the Ni NPs ranged from 2.7 to 4.7 nm, depending on the Ni loading. Under the appropriate alkaline conditions (i.e., pH 9) deprotonation of the carboxylic acid groups on the cage-type mesopore surfaces endowed the effective incorporation of Ni²⁺ precursors via favorable electrostatic interactions, and thus well-dispersed Ni NPs confined in the cage-type mesopores of SBA-16 were achieved. The combination of the cage-type mesopores and the surface functionality provided dual beneficial features to confine the immobilized Ni NPs and to tune their particle sizes. The remarkably enhanced catalytic activities of the Ni(x)@S16C materials for CO₂ hydrogenation and CH₄ formation were demonstrated. The cage-type SBA-16 support provided a positive effect for the Ni NPs to enrich the surface sites, which can strongly adsorb CO and CO₂, thus leading to high catalytic rates for CO₂ and CO hydrogenation. The reaction mechanism, catalytic kinetics, and active sites were investigated to correlate to the high reaction rate for CO₂ hydrogenation to form CH₄.

中文翻译：

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表面修饰的笼型介孔二氧化硅上可调节大小的Ni纳米颗粒，可作为高活性CO ₂加氢催化剂

在这项研究中，通过湿法浸渍，将超小镍纳米粒子（Ni NPs）可控制地支撑在-COOH官能化介孔二氧化硅SBA-16（表示为Ni（x）@ S16C，其中x为Ni含量）的笼型中孔中。在碱性条件下，然后进行热还原。Ni NP的粒径范围为2.7至4.7 nm，具体取决于Ni的负载量。在适当的碱性条件下（即pH 9），笼型介孔表面上的羧酸基团去质子化可有效结合Ni ²⁺通过有利的静电相互作用得到前驱体，从而获得了分散在SBA-16笼型中孔中的Ni NPs分散良好。笼型中孔和表面功能的结合提供了双重有益特征，以限制固定化的Ni NPs并调整其粒径。结果表明，Ni（x）@ S16C材料对于CO ₂加氢和CH ₄形成具有显着增强的催化活性。笼型SBA-16载体为Ni NP富集表面位点起到了积极作用，可以强烈吸附CO和CO ₂，从而导致对CO _2的高催化速率和一氧化碳加氢 研究了反应机理，催化动力学和活性位点，与CO ₂加氢形成CH ₄的高反应速率相关。