CHEMICAL SCIENCE

Artificial electrocatalytic reduction of carbon dioxide to synthesize amino acids


Professor Che Shun’ai of Shanghai Jiao Tong University, Professor Han Lu of Tongji University, Professor Liu Zhipan’s team of Fudan University, and Professor Zhou Zhongyue of Shanghai Jiao Tong University recently published a new study entitled “Synthesis of Amino Acids by Electrocatalytic Reduction of CO2 on Chiral Cu Surfaces” in the journal Chem.

For the first time, the research group synthesized amino acids by using chiral inorganic nanocopper materials in the electrocatalytic reduction of asymmetric carbon dioxide. The main amino acid product is serine. The mechanism of amino acid formation is attributed to the change of chiral crystals on the surface of chiral inorganic nanocopper film in the face of carbon dioxide electrocatalytic reduction pathway.

The corresponding authors of the paper are Che Shun’ai, Han Lu, Liu Zhipan, Zhou Zhongyue; The first authors are Fang Yuxi, Liu Xian, and Yang Jiuzhong.

In nature, a series of products from small molecules to biomolecules can be obtained through biological carbon sequestration and carbon dioxide reduction reactions. Although the current artificial electrocatalytic carbon dioxide reduction reaction can form polycarbon, C3+ products with multiple functional groups (such as C-N bonds and C=O bonds), especially biomolecules, cannot be realized. Based on this, Professor Che Shun’ai’s team from Shanghai Jiao Tong University, Professor Han Lu’s team from Tongji University, Professor Liu Zhipan’s team from Fudan University, and Professor Zhou Zhongyue’s team from Shanghai Jiao Tong University recently published a new study entitled “Synthesis of Amino Acids by Electrocatalytic Reduction of CO2 on Chiral Cu Surfaces” in the journal Chem. The first author is Fang Yuxi, a doctoral student at the School of Chemical Science and Engineering, Tongji University. For the first time, they synthesized amino acids by using chiral inorganic nanocopper materials in the electrocatalytic reduction of carbon dioxide. The main amino acid product is serine, and its enantiomer excess value (EE%) can exceed 90%. Moreover, it was further found that the mechanism of amino acid formation was attributed to the change of chiral crystal plane on the surface of chiral inorganic nanocopper film from thermodynamic and kinetic to the electrocatalytic reduction path of carbon dioxide. This study provides an important reference for the electrocatalytic reduction of carbon dioxide to synthesize multi-carbon products with high added value and chirality.

Copper and copper alloys are the main catalysts for the electrocatalytic reduction of carbon dioxide to synthesize multicarbon products, C1-C2 molecules and C3-4 fatty alcohols. However, CO2 reduction products containing C-N bonds are limited to C1-C2 products (urea, methylamine, and ethylamine). According to experimental and theoretical reports, the atomic configuration of the catalyst surface can improve the intrinsic catalytic activity of Cu-based catalysts for electrocatalytic carbon dioxide reduction reactions by reducing the energy barrier of the reaction pathway. However, the currently reported enhancement of catalytic activity by copper surfactant sites is only observed in C1-2 molecules and n-propanol.

Based on this, this paper applies chiral inorganic copper nanomaterials as electrocatalytic carbon dioxide reduction catalysts for the first time, and reveals the existence of chiral nanostructures and chiral surfaces (Cu(653)S) through scanning electron microscopy, transmission electron microscopy and theoretical calculations (Figure 1).

Fig. 1 Morphology and surface structure characterization of chiral inorganic copper nanofilms

The results of the synthesized chiral inorganic nanocopper membrane were further studied by the authors to study the catalytic performance of the synthesized chiral inorganic copper nanofilm, and the results are shown in Figure 2, and the faraday efficiency of ~3.8 (±0.6), ~58.6 (±6.5) and ~108.1 (±6.5) μmol of serine, ethanol and formic acid products can be obtained after 24 hours of -0.6~-1.3V vs RHE: ~1.2 (±0.2), ~22.3 (±2.5) and ~6.8 (±0.4) %. Among them, the EE% of serine can reach 94%.

Fig. 2 Electrocatalytic CO2 reduction results of chiral inorganic copper nanofilms

Through density functional theory (DFT) calculations, the authors investigated the pathway and mechanism of electrocatalytic reduction of carbon dioxide to serine (Figure 3). It is calculated that the chiral crystal plane Cu(653)S is more thermodynamically tended to form 3-hydroxypyruvate intermediate and serine, and more inclined to form L-serine, which confirms that the chiral crystal plane structure on the surface of chiral inorganic nanocopper film plays an important role in the formation of serine and enantiomeric selectivity.

Fig. 3 Electrocatalytic carbon dioxide reduction path and its Gibbs free energy

Further DFT calculations showed that chiral crystal plane Cu(653)S can also promote the formation of serine dynamically, stabilize the configuration of important intermediates H2COCOCO* and 3-hydroxypyruvic acid*, thereby reducing the activation energy and reaction barrier of H2COCOCO* hydrolysis to form 3-hydroxypyruvate*.

Fig. 4 Electrocatalytic carbon dioxide reduction kinetics

summary

In summary, this work is the first time to obtain C3+ enantiomeric amino acids containing C-N bonds by electrocatalytic reduction of carbon dioxide. It is found that the chiral crystal plane limits the configuration change of C3+ intermediates on the catalyst surface, thereby reducing the reaction energy barrier of carbon dioxide reduction synthesis of C3+ products. Although the main amino acid product is serine, the formation of a variety of amino acids and urea is also observed in the reaction, which indicates that chiral crystal plane electrocatalysis has broad application prospects for the synthesis of biomolecules. In addition, the introduction of chiral crystal planes into catalytic systems found in this work is also a powerful way to improve the intrinsic activity of catalytic materials for synthesizing C3+ products. (Source: Web of Science)

Related Paper Information:https://doi.org/10.1016/j.chempr.2022.10.017



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