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Mesoporous MnO2 nanosheets for efficient electrocatalytic nitrogen reduction via high spin polarization induced by oxygen vacancy
Nano Research 2023, 16 (4): 4664-4670
Published: 24 October 2022
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The electrochemical N2 reduction reaction (NRR) represents a green and sustainable route for NH3 synthesis under ambient conditions. However, the mechanism of N2 activation in the electrocatalytic NRR remains unclear. Herein, we found that the high spin state Mn3+-Mn3+ pairs induced by oxygen vacancy in MnO2 nanosheets greatly enhance the catalytic activities. The strong electron transfer between d orbital of Mn and orbital of N2 forces the N2 to be of radical nature, which activates the hydrogenation process and weakens the N≡N bond. Based on the density functional theory (DFT) calculation results, we precisely designed mesoporous MnO2 nanosheets with rich oxygen vacancies via using methyltriphenylphosphonium bromide (MPB) to induce more Mn3+-Mn3+ pairs (Mn3-3-MnO2), which can achieve a fairly high ammonia yield of up to 147.2 µg·h−1·mgcat−1. at −0.75 V vs. reversible hydrogen electrode (RHE) and a high Faradaic efficiency (FE) of 11%. Furthermore, these mesoporous MnO2 nanosheets exhibit the superior durability with negligible changes in both NH3 yield and FE after a consecutive 6-recycle test and the current density electrolyzed over a 24-hour period. Our findings offer an approach to designing highly active transition metal catalysts for electrocatalytic nitrogen reduction.

Research Article Issue
Mesoporous silica stabilized MOF nanoreactor for highly selective semi-hydrogenation of phenylacetylene via synergistic effect of Pd and Ru single site
Nano Research 2022, 15 (3): 1983-1992
Published: 30 September 2021
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Downloads:70

Selective semi-hydrogenation of phenylacetylene to styrene is a crucial step in the polystyrene industry. Although Pd-based catalysts are widely used in this reaction due to their excellent hydrogenation activity, the selectivity for styrene remains a great challenge. Herein, we designed a mesoporous silica stabilized Pd-Ru@ZIF-8 (MS Pd-Ru@ZIF-8) nanoreactor with novel Pd and Ru single site synergistic catalytical system for semi-hydrogenation of phenylacetylene. The nanoreactor exhibited a superior performance, achieving 98% conversion of phenylacetylene and 96% selectivity to styrene. Turnover frequency (TOF) of nanoreactor was up to as high as 2,188 h−1, which was 25 times and 5 times more than the single metal species catalysts, mesoporous silica stabilized Pd@ZIF-8 nanoreactor (MS Pd@ZIF-8), and mesoporous silica stabilized Ru@ZIF-8 nanoreactor (MS Ru@ZIF-8). This catalytic activity was attributed to the synergistic effect of Pd and Ru single site anchored strongly into the framework of ZIF-8, which reduced the desorption energy of styrene and increased the hydrogenation energy barrier of styrene. Importantly, since the ordered mesoporous silica was introduced into the nanoreactor shell to stabilize ZIF-8, MS Pd-Ru@ZIF-8 showed excellent reusability and stability. After the five cycles, the catalytical activity and selectivity still remained. This work provides insights for a synergistic catalytic system based on single-site active sites for selective hydrogenation reactions.

Research Article Issue
Plasmonic coupling-enhanced in situ photothermal nanoreactor with shape selective catalysis for C-C coupling reaction
Nano Research 2020, 13 (10): 2812-2818
Published: 05 October 2020
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Carbon-carbon (C-C) coupling reactions represent one of the most powerful tools for the synthesis of complex natural products, bioactive molecules developed as drugs and agrochemicals. In this work, a multifunctional nanoreactor for C-C coupling reaction was successfully fabricated via encapsulating the core-shell Cu@Ni nanocubes into ZIF-8 (Cu@Ni@ZIF-8). In this nanoreactor, Ni shell of the core-shell Cu@Ni nanocubes was the catalytical active center, and Cu core was in situ heating source for the catalyst by absorbing the visible light. Moreover, benefiting from the plasmonic resonance effect between Cu@Ni nanocubes encapsulated in ZIF-8, the absorption range of nanoreactor was widened and the utilization rate of visible light was enhanced. Most importantly, the microporous structure of ZIF-8 provided shape-selective of reactant. This composite was used for the highly shape-selective and stable photocatalysed C-C coupling reaction of boric acid under visible light irradiation. After five cycles, the nanoreactor still remained high catalytical activity. This Cu@Ni@ZIF-8 nanoreactor opens a way for photocatalytic C-C coupling reactions with shape-selectivity.

Research Article Issue
Highly conductive dodecaborate/MXene composites for high performance supercapacitors
Nano Research 2020, 13 (1): 196-202
Published: 18 December 2019
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Downloads:36

With the increasingly prominent energy and environmental issues, the supercapacitors, as a highly efficient and clean energy conversion and storage devices, meet the requirements well. However, it is still a challenge to enhance the capacitance and energy density of supercapacitors. A novel and highly conductive dodecaborate/MXene composites have been designed for high performance supercapacitors. The surface charge property of MXene was modified by a simple ultrasonic treatment with ammonium ion, and the dodecaborate ion can be inserted into the inner surface of MXene by electrostatic adsorption. Due to the unique icosahedral cage conjugate structure formed by the B-B bond and the highly delocalized three-dimensional π bond structure of the electrons, the negative charge is delocalied on the whole dodecaborate ion, which reduces the ability to bind to cations. Therefore, the cations can move easily, and the dodecaborate can act as a "lubricant" for ion diffusion between the MXene layers, which significantly improves the ion transfer rate of supercapacitors. The dodecaborate/MXene composites can achieve an extremely high specific capacitance of 366 F·g-1 at a scan rate of 2 mV·s-1, which is more than eight times higher than that of MXene (43 F·s-1) at the same scan rate. Our finding provides a novel route on the fabrication of the high performance supercapacitors.

Research Article Issue
Highly ordered macroporous–mesoporous Ce0.4Zr0.6O2 as dual-functional material in a polysulfide polymer
Nano Research 2018, 11 (1): 80-88
Published: 02 August 2017
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A highly hierarchically ordered macroporous–mesoporous Ce0.4Zr0.6O2 solid solution with crystalline framework walls was directly and simply prepared using polystyrene (PS) microspheres and a block copolymer as dual templates. The PS microspheres and block copolymer were assembled into colloidal crystals and mesoscopic rod-like micelles as macroporous and mesoporous templates, respectively, by a one-step process. This process offers a facile method to prepare hierarchically ordered porous materials. Compared to commercial ceria, the macroporous–mesoporous Ce0.4Zr0.6O2 material significantly improved the ultraviolet resistance and mechanical performance of a polysulfide polymer. Because the ordered macroporous–mesoporous Ce0.4Zr0.6O2 can disperse uniformly in the polysulfide polymer based on the open macroporous structure for diffusion and mobility and mesoporous structure for high surface areas. Furthermore, these results show that better-performing polysulfide polymers can be achieved by adding hierarchically structured materials.

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