Search

Understanding of the reaction network of Cu-catalyzed CO

Electrochemical conversion of light alkanes to high-value oxygenates provides an attractive avenue for eco-friendly utilization of these hydrocarbons. However, such conversion under ambient conditions remains exceptionally challenging due to the high energy barrier of C-H bond cleavage. Herein, we investigated theoretically the partial oxidation of propane on a series of single atom alloys by using active intermediates generated during water oxidation as the oxidant. We show that by controlling the potential and pH, stable surface oxygen atoms can be maintained under water oxidation conditions. The free energy barrier for C-H bond cleavage by the surface oxygen can be as small as 0.54 eV, which can be surmounted easily at room temperature. Our calculations identified three promising surfaces as effective propane oxidation catalysts. Our complementary experiments demonstrated the partial oxidation of propane to acetone on Ni-doped Au surfaces. We also investigated computationally the steps leading to acetone formation. These studies show that the concept of exploiting intermediates generated in water oxidation as oxidants provides a fruitful strategy for electrocatalyst design to efficiently convert hydrocarbons into value-added chemicals.

Harnessing renewable electricity to drive the electrochemical reduction of CO2 is being intensely studied for sustainable fuel production and as a means for energy storage. Copper is the only monometallic electrocatalyst capable of converting CO2 to value-added products, e.g., hydrocarbons and oxygenates, but suffers from poor selectivity and mediocre activity. Multiple oxidative treatments have shown improvements in the performance of copper catalysts. However, the fundamental underpinning for such enhancement remains controversial. Here, we combine reactivity, in-situ surface-enhanced Raman spectroscopy, and computational investigations to demonstrate that the presence of surface hydroxyl species by co-electrolysis of CO2 with low concentrations of O2 can dramatically enhance the activity of copper catalyzed CO2 electroreduction. Our results indicate that co-electrolysis of CO2 with an oxidant is a promising strategy to introduce catalytically active species in electrocatalysis., While the electrochemical conversion of CO2 to highly reduced products is unique to copper, there are still gaps in understanding copper catalysts’ efficacy. Here, authors find that co-electrolysis of CO2 with O2 can enhance copper’s catalytic activities.

K-ion batteries (KIBs) have attracted considerable attention because of their unique advantages. Manganese-containing electrode materials have poor cycle performance due to the dissolution of manganese in the electrolyte. Here, manganese-containing KIB cathode with a yolk–shell structure is synthesised by a homogeneous precipitation method. In addition, large charge–discharge capacity and good cycle stability are obtained. Electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) are used to understand the improvement in the electrochemical performance caused by the developed material. Due to the volume-buffering effect, the yolk–shell structure does not cause particle rupture, which helps form a stable solid–electrolyte interface (SEI) film. This reduces the number of Mn ions exposed to the electrolyte and results in long-term cycle stability. This work provides a universal route to improve the cycling performance of manganese-containing cathode for KIBs applications.

Carbon encapsulated nanosheet-assembled MoS2 (C@MoS2) nanospheres have been synthesized using poly(vinylpyrrolidone) (PVP) as surfactant and carbon source via hydrothermal approach in combination with high-temperature calcination process. PVP plays an important role in the formation of nanosheet-assembled MoS2 nanospheres, which can be in-situ converted into amorphous carbon to encapsulate MoS2. When evaluated for electrochemical lithium storage properties, the C@MoS2 nanospheres exhibit enhanced electrochemical energy storage performances compared to the bare MoS2 nanosheets, including high specific capacity (1135.8 mAh g−1 at 0.1 A g−1), excellent rate capability (384.4 mAh g−1 at 8 A g−1 and 330.5 mAh g−1 at 10 A g−1), and good cycling stability (97.03% capacity retention after 100 cycles at 0.5 A g−1). The enhanced lithium storage performances of the C@MoS2 nanospheres can be ascribed to the boosted electronic conductivity arising from PVP derived carbon, and the facilitated lithium ion transport due to the shorter diffusion length of MoS2 nanosheet-assembled structures.

To establish the method of determination of 3-monochloropropane-1,2-diol( 3-MCPD) in grease food by gas chromatography-mass spectrometry( GC-MS).3-MCPD in grease food represented by bean paste was extracted by ultrasound,purified by alkaline earth solid phase extraction column,derivatived using phenylboronic acid( PBA) and detected by GC-MS.The linearity of 3-MCPD ranged from 1-100 ng/mL,with correlation coefficient at 0. 9993.The limits of quantitation( LOQ) in soy sauce,bean paste,pepper oil were 0. 6,0. 5 and7. 0 μg/kg and limits of detection( LOD) were 1. 9,1. 6 and 18. 8 μg/kg,respectively.Average recovery rate and relative standard deviation was 78. 3%-106. 7% and 1. 9%-11. 6%( n = 6), when 3-MCPD was added in grease food at 2. 5-1000 μg/kg.The method has good purification effect and the detection sensitivity and accuracy,and can be used for the determination of 3-MCPD in grease food.

Ti3+ self-doped Li4Ti5O12 (S-LTO) nanosheets have been synthesized via a facile solvothermal approach combined with hydrogenation treatment. The thickness and lateral dimension of Li4Ti5O12 nanosheets are 10–20 nm and 100–400 nm, respectively. The Ti3+ species and/or oxygen vacancies are well introduced into the crystal structures of Li4Ti5O12 after hydrogen reduction, resulting into an enhancement in the electronic conductivity and the modified surface electrochemical activity. When evaluated for lithium storage capacity, the S-LTO nanosheets exhibit enhanced electrochemical energy storage performances compared to the pristine Li4Ti5O12 (P-LTO) nanosheets, including high capacity (165.6 mA h g−1 at 0.5 C), excellent rate capability (119.6 mA h g−1 at 20 C), and good cyclic stability (95.3% capacity retention after 100 cycles at 10 C). The improvement of lithium storage performances is ascribed to the increased electronic conductivity and the shortened lithium ion diffusion paths arising from the introduction of Ti3+ species and the ultrathin thickness of S-LTO.