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5. The effects of halide anions on the electroreduction of CO2 to C2H4: a density functional theory study

Author

Ma, Xifei, Xing, Lu, Yao, Xiaoqian, Zhang, Xiangping, Liu, Lei, and Zhang, Suojiang

Subjects
Physics - Chemical Physics
Abstract

The halide anions present in the electrolyte gradually improves the Faradaic efficiencies (FEs) of the multi-hydrocarbon (C2+) products for the electrochemical reduction of CO2 over copper (Cu) catalysts in the order of F- < Cl- < Br- < I-. However, the mechanism behind the increased yield of C2+ products with the addition of halide anions still remains indistinct. In this study, we analysed the mechanism by investigating the electronic structures and computing the relative free energies of intermediates formed from CO2 to C2H4 on the Cu (100) facet based on density functional theory (DFT) calculations. The results show that formyl *CHO species from the hydrogenation reaction of the adsorbed *CO acts as the key intermediate, and the C-C coupling reaction occurs preferentially between the *CHO and *CO with the formation of a *CHO-CO intermediate. Subsequently, the free-energy pathway of C2H4 formation has been proposed, and we found that the presence of halide anions significantly decreases the free energy of the *CHOCH intermediate, and enhances the desorption capacity of C2H4 in the order of F- < Cl- < Br- < I-. Lastly, the obtained results are rationalized by the Bader charge analysis.

Published
2021

10. Anti-electrostatic hydrogen bonding between anions of ionic liquids: A density functional theory study

Author

Chen, Junwu, Dong, Kun, Liu, Lei, Zhang, Xiangping, and Zhang, Suojiang

Subjects
Physics - Chemical Physics
Abstract

Hydrogen bonds (HBs) play a crucial role in the physicochemical properties of ionic liquids (ILs). At present, HBs between cations and anions (Ca-An) or between cations (Ca-Ca) in ILs have been reported extensively. Here, we provided DFT evidences for the exists of HBs between anions (An-An) in the IL 1-(2-hydroxyethyl)-3-methylimidazolium 4-(2-hydroxyethyl)imidazolide [HEMIm][HEIm]. The thermodynamics stabilities of anionic, cationic, and H2O dimers together with ionic pairs were studied by potential energy scans. The results show that the cation-anion pair is the most stable one, while the HB in anionic dimer possesses similar thermodynamics stability to the water dimer. The further geometric, spectral and electronic structure analyses demonstrate that the inter-anionic HB meets the general theoretical criteria of traditional HBs. The strength order of four HBs in complexes is cation-anion pair > H2O dimer = cationic dimer > anionic dimer. The energy decomposition analysis indicates that induction and dispersion interactions are the crucial factors to overcome strong Coulomb repulsions, forming inter-anionic HBs. Lastly, the presence of inter-anionic HBs in ionic cluster has been confirmed by a global minimum search for a system containing two ionic pairs. Even though hydroxyl-functionalized cations are more likely to form HBs with anions, there still have inter-anionic HBs between hydroxyl groups in the low-lying structures. Our studies broaden the understanding of HBs in ionic liquids and support the recently proposed concept of anti-electrostatic HBs.

Published
2020
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11. Theoretical evidence for new adsorption sites of CO$_2$ on the Ag electrode surface

Author

Guo, Shuai, Li, Yao, Liu, Lei, Zhang, Xiangping, and Zhang, Suojiang

Subjects
Physics - Chemical Physics
Abstract

Nowadays, electrochemical reduction of CO$_2$ has been considered as an effective method to solve the problem of global warming. The primary challenge in studying the mechanism is to determine the adsorption states of CO$_2$, since complicated metal surfaces often result in many different adsorption sites. Based on the density functional theory (DFT) calculations, we performed a theoretical study on the adsorption of CO$_2$ on the Ag electrode surface. The results show that the adsorption populations of CO$_2$ are extremely sensitive to the adsorption sites. Importantly, we found that the preferable adsorption positions are the terrace sites, rather than the previous reported step sites. The adsorption populations were found with the order of (211) > (110) > (111) > (100). Subsequently, the adsorption characteristics were correlated with the d-band theory and the charge transfers between Ag surfaces and CO$_2$.

Published
2020

14. Sequential drug release via chemical diffusion and physical barriers enabled by hollow multishelled structures.

Author

Zhao, Decai, Yang, Nailiang, Wei, Yan, Jin, Quan, Wang, Yanlei, He, Hongyan, Yang, Yang, Han, Bing, Zhang, Suojiang, and Wang, Dan

Subjects
Escherichia coli, Thiazoles, Delayed-Action Preparations, Drug Carriers, Anti-Bacterial Agents, Microbial Sensitivity Tests, Drug Compounding, Microspheres, Diffusion, Nanostructures, Drug Liberation
Abstract

Hollow multishelled structures (HoMSs), with relatively isolated cavities and hierarchal pores in the shells, are structurally similar to cells. Functionally inspired by the different transmission forms in living cells, we studied the mass transport process in HoMSs in detail. In the present work, after introducing the antibacterial agent methylisothiazolinone (MIT) as model molecules into HoMSs, we discover three sequential release stages, i.e., burst release, sustained release and stimulus-responsive release, in one system. The triple-shelled structure can provide a long sterility period in a bacteria-rich environment that is nearly 8 times longer than that of the pure antimicrobial agent under the same conditions. More importantly, the HoMS system provides a smart responsive release mechanism that can be triggered by environmental changes. All these advantages could be attributed to chemical diffusion- and physical barrier-driven temporally-spatially ordered drug release, providing a route for the design of intelligent nanomaterials.

Published
2020

29. Electro‐Driven Multi‐Enzymatic Cascade Conversion of CO2 to Ethylene Glycol in Nano‐Reactor.

Author

Luan, Likun, Zhang, Yingfang, Ji, Xiuling, Guo, Boxia, Song, Shaoyu, Huang, Yuhong, and Zhang, Suojiang

Subjects
ETHYLENE glycol, ALCOHOL dehydrogenase, CARBON dioxide, ENZYMES, FORMALDEHYDE, NAD (Coenzyme)
Abstract

Multi‐enzymatic cascade reaction provides a new avenue for C─C coupling directly from CO2 under mild conditions. In this study, a new pathway with four enzymes including formate dehydrogenase (PaFDH), formaldehyde dehydrogenase (BmFADH), glycolaldehyde synthase (PpGALS), and alcohol dehydrogenase (GoADH) is developed for directly converting CO2 gas molecules to ethylene glycol (EG) in vitro. A rhodium‐based NADH regeneration electrode is constructed to continuously provide the proton and electron of this multi‐enzymatic cascade reaction. The prepared electrode can reach the Faradaic Efficiency (FE) of 82.9% at −0.6 V (vs. Ag/AgCl) and the NADH productivity of 0.737 mM h−1. Shortening the reaction path is crucial for multi‐enzymatic cascade reactions. Here, a hydrogen‐bonded organic framework (HOF) nano‐reactor is successfully developed to immobilize four enzymes in one pot with a striking enzyme loading capacity (990 mg enzyme g−1 material). Through integrating and optimization of NADH electro‐regeneration and enzymatic catalysis in one pot, 0.15 mM EG is achieved with an average conversion rate of 7.15 × 10−7 mmol CO2 min−1 mg−1 enzymes in 6 h. These results shed light on electro‐driven multi‐enzymatic cascade conversion of C─C coupling from CO2 in the nano‐reactor. [ABSTRACT FROM AUTHOR]

Published
2024
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