CHEMICAL SCIENCE

The researchers report a novel high-voltage coupling chemical reaction


Chemical reactions refer to the process by which molecules break into atoms, and atoms are arranged and combined into new molecules. Under the high pressure condition above 10,000 atmospheres (1GPa), the activation energy, reaction enthalpy and enthalpy of formation of chemical reactions will change significantly with the increase of pressure. Under the action of high-pressure inhibition product decomposition and phase regulation, some chemical reactions that cannot be carried out under atmospheric pressure conditions can occur under high pressure. High-pressure chemical reactions open a new channel for unconventional chemical synthesis.

Recently, the Lei Li research group of the Institute of Atomic and Molecular Physics of Sichuan University reported a new high-pressure coupling reaction (HPC) in the journal Inorganic Chemistry of the American Chemical Society. In this paper, a novel coupling reaction path occurs under high pressure conditions, coupling two chemical reactions with high and low barriers, and realizing the synthesis of rhenium nitride bulk materials under mild synthesis conditions.

The preparation of new rhenium nitride bulk materials has always been one of the frontier topics in the field of unconventional chemical synthesis. Rhenium nitride synthesized by laser heating diamond anvil (LHDAC) method has a pressure of at least 140,000 atmospheres or more, and rhenium nitride is usually a micron-level product. Rhenium nitride-based bulk composites were prepared by coupling high-pressure solid-phase metathesis reaction (HPSSM) by high-pressure coupling chemical reaction method, and RexN/Fe3N spherical bulk composites (>2 mm) were synthesized at pressure of 100,000-150,000 atmospheres and 1800 K.

High-pressure solid-phase metathesis is a new high-pressure chemical reaction discovered by Lei Li and He Duanwei in 2009. The reaction realizes the conversion from metal oxides to metal nitrides through ion substitution behavior under high pressure, so as to synthesize a variety of high-quality metal nitrides. For example, the formation of Fe3N between FeOOH and BN is a typical high-pressure solid-phase metathesis reaction:

Equation 1 .png

(1)

In this high-pressure solid-phase metathesis reaction, free nitrogen ions can be formed, which easily react with metals to form metal nitrides. The synthesis strategy of high-pressure coupling reaction is to add metal elemental rhenium (Re) to the precursor of high-pressure solid-phase metathesis reaction, so that rhenium atoms directly participate in the intermediate stage of formula (1), “ride the free ride of high-pressure solid-phase metathesis reaction”, combine with free nitrogen ions and directly participate in the nitriding reaction to form rhenium nitrogen compounds:

Equation 2 .png

(2)

Since rhenium is “hitchhiking” to the terminal (metal nitriding), the reaction barrier of rhenium nitriding is significantly reduced. Therefore, the synthesis pressure of Re3N and Re2N is reduced from 13 GPa and 20 GPa to 10 GPa, respectively, forming a 2-3 mm spherical bulk RexN/Fe3N composite (2≤x≤3). The newly discovered high-pressure coupling reaction has important implications for understanding the ion exchange mechanism at high pressure and chemical synthesis under unconventional conditions.

Picture 2 .png

The original paper on high-pressure coupling reactions was published in Inorganic Chemistry under the title “High-pressure coupling reactions to produce a spherical bulk RexN/Fe3N Composite.” Master student Zhang Hengyuan is the first author of the paper, and the Institute of Atomic and Molecular Physics of Sichuan University is the first author of the paper. The collaborators include the Key Laboratory of Superhard Materials of Jilin University, the Geodynamics Research Center of Ehime University in Japan, and the School of Physics of Sichuan University. (Source: Sichuan University)

Related paper information:https://doi.org/10.1021/acs.inorgchem.2c04089

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