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Hydrazine hydrate as a hydrogen source has a good effect on nitro reduction, but overuse has environmental toxicity and is prone to over‐hydrogenation, resulting in low selectivity. Herein, we report a magnetically separable Rh/Fe3O4 (1.26 wt%) catalyst containing an optimal Rh content that can completely convert 3‐nitrostyrene to 3‐vinylaniline (> 99% selectivity) using a stoichiometric molar ratio of hydrazine hydrate (‐NO2:N2H4·H2O = 1:1.5). This is due to the synergy between Rh and Fe3O4 and the natural selectivity of N2H4·H2O for nitro. The synergy can reduce the activation energy of the reaction (36.6 kJ/mol), increasing the reduction rate of nitro group and avoiding the combination of active hydrogen species (H*) to H2 as well as the hydrogenation of N2H4 to NH3. Moreover, the active H* produced by N2H4·H2O is different from that produced by H2, and excess dose of N2H4 will inevitably yield H2 thus decline the selectivity. [ABSTRACT FROM AUTHOR]

The nanoconfinement approach for constructing ultra‐small nanoparticles has been effectively utilized in the development of non‐precious metal catalysts. Herein, the catalyst precursor was prepared by host‐guest assembly method, using PCN‐222 as the host and 1,1′‐bis(diphenylphosphino) ferrocene (DPPF) as the guest. After calcination, the sub‐2 nm iron oxide nanoparticles within a phosphorus‐nitrogen co‐doped carbon matrix (Fe3O4@P/N‐CDCM) was obtained. Benefiting from the nanoconfinement effect, the sub‐2 nm Fe3O4 nanoparticles were uniformly dispersed on the P/N‐CDCM matrix. As a representative application, Fe3O4@P/N‐CDCM‐600 showed remarkable catalytic activity in the reduction of various nitroaromatic compounds. Under ambient conditions, the efficient reduction of nitro compounds in aqueous solution led to excellent conversion rates (96–99 %) and selectivity (99 %) within 45 minutes. Additionally, the catalyst maintained high efficiency over 5 cycles without experiencing a noticeable decrease in activity. This work provides an innovative and cost‐effective strategy for fabricating highly dispersed non‐precious metal nanoparticles. [ABSTRACT FROM AUTHOR]

Organic cathode materials for aqueous rechargeable zinc batteries (ARZBs) are rapidly gaining prominence, while the exploration of compounds with affordable synthesis, satisfactory electrochemical performance, and understandable mechanisms still remains challenging. In this study, 6,8,15,17‐tetraaza‐heptacene‐5,7,9,14,16,18‐hexaone (TAHQ) as an easily synthesized organic cathode material with novel quinone/pyrazine alternately conjugated molecule structure is presented. This organic electrode exhibits good capacity with highly reversible redox reactions, and the influence of multi‐active structures on the Zn2+/H+ loading behavior is systematically investigated by ex situ spectroscopy, electrochemical tests, and computation. Both experimental and theoretical studies effectively address the Zn2+/H+ intercalation/deintercalation kinetics. Benefitting from the fused active functionalities, the assembled Zn//TAHQ battery displays a maximum discharge specific capacity of 254.3 mAh g−1 at 0.5 A g−1, and it maintains remarkable cycle performance with 71% capacity retention after 1000 cycles under 5 A g−1. [ABSTRACT FROM AUTHOR]

BACKGROUND Tin ore is a hard-to-decompose mineral. The main form is cassiterite (SnO2), and there are many symbiotic and associated elements. The commonly used acid-digestion method can barely dissolve SnO2, making it difficult for accurate measurement of symbiotic and associated elements in tin ore. OBJECTIVES To decompose the tin ore completely, and accurately determine the symbiotic and associated trace elements in ore. METHODS Hydrogen iodide can be produced in a non-aqueous state during the melting of ammonium iodide at a lower temperature, and the acidity of hydrogen iodide and the reductive decomposition of SnO2 by ammonia, and Sn separation by the sublimation of SnI4 which is the basis of the study. Under the catalysis of a high purity platinum, ammonium iodide was used to decompose cassiterite for 30 minutes in a Maffer furnace at 450℃. Tin was removed in the form of SnI4 with a removal rate of 98%. The residue was dissolved by 2 mL HF and 1 mL HNO3 using pressurized acid digestion. Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was used to accurately determine 24 elements in tin ore. RESULTS The element detection limits are from 0.001 to 2.9 μg/g, and more than 90% of the elements have a relative standard deviation (RSD) of less than 5%. The relative error is less than 10%. CONCLUSIONS The method solves the problem of tin ore being difficult to decompose, can measure the coexisting metal elements, and is also suitable for determining trace and ultra-trace elements in tin ore with Sn contents between 1.27% and 62.49% and trace elements in tin concentrate.

Copper in copper ores is commonly determined by a manual visual titration method. The method has large errors, poor precision and poor reliability due to the need to gauge the end of the chemical reaction by a chemical indicator. Based on these disadvantages, a high precision determination method for high Cu content in Cu ores has been developed. In this new method, the terminal point is determined by intelligent potentiometric titrator automatically and the amount of sodium thiosulfate standard solution is accurate to 0.001 mL by a high-resolution dosing device. Moreover, the amount of potassium iodide is increased to eliminate the absorption of iodine with copper iodide which was produced during titration, as the copper iodide can be dissolved by high concentrations of iodide. National standard materials such as copper concentrate, chalcopyrite and lead brass with copper content ranging from 24.2% to 59.09% are determined using this method. The relative standard deviation is lower than 0.3%(n=10). The extreme differences are 0.13%, 0.21% and 0.29%, better than manual visual titration. The proposed method improves the automation for accurate determination of ores with Cu content greater than 0.5%, especially for those with Cu content more than 10%.