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Research on metal-organic framework (MOF)-based non-enzymatic glucose sensors usually ignores the impact of the surface reconstruction degree of MOF on the activity of catalyzing glucose oxidation. In this work, we choose zeolitic imidazolate framework-67 (ZIF-67), which is commonly used in glucose sensing, as a representative to investigate the influence of reconstruction degree on its structure and glucose catalytic performance. By employing the electrochemical activation strategy, the activity of ZIF-67 in catalyzing glucose gradually increased with the prolongation of the activation time, reaching the optimum after 2 h activation. The detection sensitivity of the activated ZIF-67 was 19 times higher than that of the initial ZIF-67, and the limit of detection (LOD) was lowered from 7 to 0.4 µM. Our findings demonstrate that the oxidation degree of ZIF-67 deepened rapidly with continuously activation and was basically reconstructed to CoOOH after 2 h activation, accompanied by a morphological change from cuboctahedral to flower-like. Simultaneously, theoretical investigation revealed that ZIF-67 is not suitable as a stable glucose sensor electrode since the adsorbed glucose molecules hasten the dissociation of ligands and the breaking of Co–N bond in ZIF-67. Therefore, our work has important implications for the rational design of next-generation MOF-based glucose sensors. [ABSTRACT FROM AUTHOR]

As the main limiting step of overall water splitting, oxygen evolution reaction (OER) is urgent to be enhanced by developing efficient catalysts to promote the process of electrolytic water. Based on theoretical analysis, the Ni-metal-organic framework (Ni-MOF) and NiFe-layered double hydroxide (NiFe-LDH) (NiFe-LDH/MOF) heterostructure can optimize the energy barrier of the OER process and decrease the adsorption energy of oxygen-containing intermediates, effectively accelerating the OER kinetics. Accordingly, layered NiFe-LDH/MOF heterostructures are in situ constructed through a facile two-step reaction process, with substantial oxygen defects and lattice defects that further improve the catalytic performance. As a result, only 208 and 275 mV OER overpotentials are needed for NiFe-LDH/MOF to drive the current densities of 20 and 100 mA·cm−2 in 1 M KOH solutions, and even maintain catalytic stability of 100 h at 20 mA·cm−2. When applied to seawater oxidation, only 235 and 307 mV OER overpotentials are required to achieve the current densities of 20 and 100 mA·cm−2, respectively, with almost no attenuation for 100 h stability test at 20 mA·cm−2, all better than commercial RuO2. This work provides the theoretical and experimental basis and a new idea for efficiently driving fresh water and seawater cracking by heterostructure and defect coupling design toward catalysts. [ABSTRACT FROM AUTHOR]

To decrease the contaminant leaching and radon exhalation from uranium tailings, a phosphoric acid-based geopolymer (PAG) precursor was selected as a solidifying agent to bind coarse sands to achieve compact structures. Machine learning was applied to explore the optimal ratio of geopolymer preparation, aimed at achieving a higher compressive strength of solidified bodies. Results showed that the maximum compressive strength of 18.964 MPa appeared at the mass ratio of 2.8 for phosphoric acid/kaolin. The uranium leaching rate of 0.70 × 10−6 cm/d on the 42nd day was three orders of magnitude less than the clay mixture-based geopolymer solidified bodies. The successful synthesis of geopolymer was evidenced by the X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), the homogeneous and dense structure of solidified bodies was characterized by the scanning electron microscopy (SEM). [ABSTRACT FROM AUTHOR]

Iron-based oxygen reduction reaction (ORR) catalysts have been the focus of research, and iron sources play an important role for the preparation of efficient ORR catalysts. Here, we successfully use LiFePO4 as ideal sources of Fe and P to construct the heteroatom doped Fe-based carbon materials. The obtained Fe-N-P co-doped coral-like carbon nanotube arrays encapsulated Fe2P catalyst (C-ZIF/LFP) shows very high half-wave potential of 0.88 V in alkaline electrolytes toward ORR, superior to Pt/C (0.85 V), and also presents a high half-wave potential of 0.74 V in acidic electrolytes, comparable to Pt/C (0.8 V). When further applied into a home-made Zn-air battery as cathode, a peak power density of 140 mW·cm2 is reached, exceeds commercial Pt/C (110 mW·cm2). Besides, it also presents exceptional durability and methanol resistance compared with Pt/C. Noticeably, the preparation method of such a high-performance catalyst is simple and easy to optimize, suitable for the large-scale production. What's more, it opens up a more sustainable development scenario to reduce the hazardous wastes such as LiFePO4 by directly using them for preparing high-performance ORR catalysts. [ABSTRACT FROM AUTHOR]