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Carbon charge population and oxygen molecular transport regulated by program-doping for highly efficient 4e-ORR
No full textOxygen reduction reaction (ORR) is a key reaction in both hydrogen peroxide (H2O2) generation and fuel cells system. Carbon is a promising catalyst to overcome the sluggish kinetics of ORR, while its intrinsic activity is contentious. It has been verified that both heteroatoms doping and intrinsic defects upgrade the carbon performance. Nevertheless, the charge population is the fundamental origin of carbon activity. In this work, N and S are used to co-regulate the carbon charge population. Results demonstrate that the N in the six-member ring and thiophene-S are electron-withdrawing configurations, leading to more positive charge distribution. Nevertheless, pyrrole-N is an electron-donor and destroys the charge delocalization when it co-existed with a six-member N ring or thiophene-S. Consequently, S is preferentially released to inhabit the five-membered ring formation site, inducing the precise formation of six-membered N ring. Importantly, the transfer enhancement of O-2 molecules by physical absorption and reaction consumption is confirmed by in-situ concentration detection. The synthesized material possesses more positive half-wave potential (E-1/2~0.851 VRHE), high selectivity and stability than that of Pt/C (E-1/2~0.823 VRHE)
Carbon charge population and oxygen molecular transport regulated by program-doping for highly efficient 4e-ORR
No full textOxygen reduction reaction (ORR) is a key reaction in both hydrogen peroxide (H2O2) generation and fuel cells system. Carbon is a promising catalyst to overcome the sluggish kinetics of ORR, while its intrinsic activity is contentious. It has been verified that both heteroatoms doping and intrinsic defects upgrade the carbon performance. Nevertheless, the charge population is the fundamental origin of carbon activity. In this work, N and S are used to co-regulate the carbon charge population. Results demonstrate that the N in the six-member ring and thiophene-S are electron-withdrawing configurations, leading to more positive charge distribution. Nevertheless, pyrrole-N is an electron-donor and destroys the charge delocalization when it co-existed with a six-member N ring or thiophene-S. Consequently, S is preferentially released to inhabit the five-membered ring formation site, inducing the precise formation of six-membered N ring. Importantly, the transfer enhancement of O-2 molecules by physical absorption and reaction consumption is confirmed by in-situ concentration detection. The synthesized material possesses more positive half-wave potential (E-1/2~0.851 VRHE), high selectivity and stability than that of Pt/C (E-1/2~0.823 VRHE)
Lithium-ion transfer strengthened by graphite tailings and coking coal for high-rate performance anode
No full textDue to the anisotropy of natural graphite crystal structure, the lithium-ion transfer efficiency is poor at large current density for graphite anode. To solve this problem, the composite anode was prepared by co-pyrolysis of coking coal and graphite tailings. Results showed that the liquid plastic mass produced by coking coal pyrolysis not only realized the lamellar reconstruction of graphite tailings, but also strengthened the isotropy of the composite anode material, and the N and S heteroatoms in semi-coke strengthened the transmission of lithium ions. Compared with anode of graphite tailings (SGD), the rate capacity retention of the anode from the co pyrolysis of oxidized graphite tailings and coking coal (OSGD-GLM) demonstrated superior rate performance (capacity retention increased from 13.98% to 32.00% at current density of 5.0 A g(-1) compared to 0.1 A g(-1)), long-term stability and excellent full cell rate performance. More importantly, the lithium-ion diffusion coefficient of OSGD-GLM under charging state was measured by galvanostatic intermittent titration (GITT), which was in the range between 6.26 x 10(-10) and 1.71 x 10(-8) cm2 s(-1), significantly higher than that of commercial graphite anode
Crystallization behavior of calcium silicate hydrate in highly alkaline system: Structure and kinetics
No full textDuring utilization of high silicon solid wastes, a characteristic and complex desilication solution (DSS) generated, remains an important subject to be as precursor of calcium silicate hydrate (C-S-H) crystallization. By using the mixed suspension mixed product removal (MSMPR) crystallizer, the crystallization behavior of C-S-H in DSS was investigated. The effects of temperature, initial Ca/Si ratio, silicate concentrations, solvent alkalinity on the morphology and structure of synthesized C-S-H were investigated through X-ray diffraction, scanning electron microscopy, laser particle size analyzer, and 29Si magic angle spinning nuclear magnetic resonance. The crystallization growth rate and particle size of C-S-H were positively correlated with temperature. The elevation of Ca/Si molar ratio will lead to shortening of the silicate chain to form more monomers. The increase of silicate concentration and solvent alkalinity will result in the formation of shorter silicate chains. This work provides theoretical guidance for precise preparation and design of C-S-H synthesized by a causticization strategy
<p>Enhancing dimethyldichlorosilane production in Rochow-Muller reaction by adding ZnO-Sn-P co-promoter in CuO/SiO2</p>
No full textCommercial nonsupported Cu-based catalysts have to be mixed with various promoters to enhance their catalytic performance in the Rochow-Muller reaction. However, considerable debates still exist at a fundamental level on how these promoters function. Herein, we systematically investigated the effects of ZnO, Sn, and P promoters on the catalytic property of the CuO/SiO2 catalyst for synthesizing dimethyldichlorosilane (M2) via the Rochow-Muller reaction. A series of CuO/SiO2 catalysts containing these promoters were prepared by the ball-milling method. The CuO/SiO2 catalyst with the coexistence of ZnO, P, and Sn promoters showed the highest catalytic activity, even superior to the commercial non supported Cu-based catalysts. Detailed characterizations showed the increased capability for oxygen adsorption on the CuO surface and dissociative chemisorption of methyl chloride led to the improved catalytic performance. This work deciphers the promoter mechanism and demonstrates a promising strategy for the efficient synthesis of M2.(C) 2022 Elsevier Inc. All rights reserved
