Enhancing Photocatalytic CO2 Conversion through Oxygen-Vacancy-Mediated Topological Phase Transition.

Weak adsorption of gas reactants and strong binding of intermediates present a significant challenge for most transition metal oxides, particularly in the realm of CO2 photoreduction. Herein, we demonstrate that the adsorption can be fine-tuned by phase engineering of oxide catalysts. An oxygen vacancy mediated topological phase transition in Ni-Co oxide nanowires, supported on a hierarchical graphene aerogel (GA), is observed from a spinel phase to a rock-salt phase. Such in situ phase transition empowers the Ni-Co oxide catalyst with a strong internal electric field and the attainment of abundant oxygen vacancies. Among a series of catalysts, the in situ transformed spinel/rock-salt heterojunction supported on GA stands out for an exceptional photocatalytic CO2 reduction activity and selectivity, yielding an impressive CO production rate of 12.5 mmol g-1 h-1 and high selectivity of 96.5 %. This remarkable performance is a result of the robust interfacial coupling between two topological phases that optimizes the electronic structures through directional charge transfer across interfaces. The phase transition process induces more Co2+ in octahedral site, which can effectively enhance the Co-O covalency. This synergistic effect balances the surface activation of CO2 molecules and desorption of reaction intermediates, thereby lowering the energetic barrier of the rate-limiting step.

Mechanism of synergistic removal of NO and SO2 by sodium bicarbonate.

Sodium bicarbonate (NaHCO3) is considered to be an effective alkaline adsorbent for SO2 removal and surprisingly, the concentration of NO is significantly reduced along with the generation of NO2 during its desulfurization. Unfortunately, the mechanism of NO interaction with NaHCO3, SO2 and O2 is ambiguous. In this work, the effects of absorption gas and absorber composition on SO2/NO absorption performance were explored, the absorption products were characterized using XPS and SEM, and the Gibbs free energy of the inferred reaction path was calculated based on density functional theory (DFT). The results showed that SO2 and O2 synergistically promoted the absorption and removal of NO by NaHCO3, which could completely remove SO2 and absorb 90% of NO at 160 °C. Sodium metabisulfite (Na2S2O5) and sodium dithionate (Na2S2O6) were identified as the active substances responsible for efficient NO absorption, and the oxidation of Na2S2O5 to Na2S2O6 is the controlling step of the NO removal reaction. Specifically, Na2S2O5 is an intermediate produced by the reaction of NaHCO3 with SO2, and subsequently reacts with O2 to produce Na2S2O6, which releases reactive oxygen species to oxidize NO to NO2. In addition, when the S/N ratio is greater than 1 and the O2 content is greater than 5%, both SO2 and NO can maintain removal efficiency higher than 90%, indicating that the absorption reaction of SO2 and NO by NaHCO3 is highly adaptable to the flue gas composition.

Simultaneously enhanced stability and biological activities of chlorogenic acid by covalent grafting with soluble oat ß-glucan.

Chlorogenic acid (CA) has a wide range of biological activities but the chemical structure is extremely unstable. In this study, CA was grafted onto a soluble oat ß-glucan (OßGH) to improve the stability. Although the crystallinity and thermal stability of CA-OßGH conjugates reduced, the storage stability of CA significantly improved. The DPPH and ABTS scavenging ability of CA-OßGH IV (graft ratio 285.3 mg CA/g) were higher than 90 %, which is closed to activities of equivalent concentration of Vc (93.42 %) and CA (90.81 %). The antibacterial abilities of CA-OßGH conjugates are improved compared to the equivalent content of CA and potassium sorbate. Particularly, the inhibition rate of CA-OßGH for gram-positive bacteria (Staphylococcus aureus and Listeria monocytogenes) are significantly higher than that of gram-negative bacteria (Escherichia coli). The results demonstrated that covalent grafted CA with soluble polysaccharide is an effective strategy to enhance its stability and biological activities.

Preparation and characterization of feruloylated oat ß-glucan with antioxidant activity and colon-targeted delivery.

Ferulic acid (FA) is an effective chemopreventive and therapeutic agent for colorectal cancer. However, FA cannot stably reach the colon through human digestive system, and it can be grafted into oligosaccharides to improve its digestion stability. Therefore, in this study, different degrees of substitution of feruloylated oat ß-glucan (FA-OßG) were prepared by grafting FA onto water soluble oat ß-glucan. FA grafting changed the crystallinity and surface morphology of OßG, and the thermal stability of the FA-OßG improved. As the DS increased, the antioxidant activity of FA-OßG increased, and FA-OßG III with DS of 0.184 showed the same antioxidant activities compared to the equal amount of free FA. The FA-OßG showed higher stability under gastrointestinal and colonic conditions than free FA. Furthermore, the FA-OßG conjugates exhibited good in vitro anticancer activity against human colorectal cancer cells, while FA-OßG III showed better anticancer activity than an equal amount of free FA.

The combined effect of protein hydrolysis and Lactobacillus plantarum fermentation on antioxidant activity and metabolomic profiles of quinoa beverage.

Lactic acid bacteria fermentation is a commonly applied technique to produce nutritional, functional, and organoleptic enhanced foods. In the present study, protein hydrolysis and Lactobacillus plantarum fermentation were coupled to develop quinoa beverages. Protein hydrolysis effectively promoted the growth and fermentation of L. plantarum. Fermentation alone did not significantly improve antioxidant activity, but the combined use of protein hydrolysis and L. plantarum fermentation significantly improved the antioxidant activity of the quinoa beverage. Nontargeted metabolomics based on UHPLC-Q Exactive HF-X/MS and multivariate statistical analysis were performed to reveal the metabolite profile alterations of the quinoa beverage by different processing methods. A total of 756 metabolites were identified and annotated, which could be categorized into 12 different classes. The significant differentially abundant metabolites were mainly involved in primary metabolite metabolism and secondary metabolite biosynthesis. Many of these metabolites were proven to be vitally important to the function and taste formation of the quinoa beverage. Most importantly, the coupled use of protein hydrolysis and L. plantarum fermentation significantly increased some functional ingredients compared with protein hydrolysis and L. plantarum fermentation alone. The above results indicate that protein hydrolysis coupled with L. plantarum fermentation is an effective strategy to develop functional quinoa beverages.

The Efficiency of Lemon Essential Oil-Based Nanoemulsions on the Inhibition of Phomopsis sp. and Reduction of Postharvest Decay of Kiwifruit.

Essential oils (EOs) have excellent antibacterial activity and are generally recognized as safe (GRAS) for use in food preservatives. However, the application of EOs is limited because of their strong volatility and easily oxidized. Encapsulation of EOs into nanoemulsions could effectively prevent oxidative deterioration. In this study, lemon essential oil-based nanoemulsion (LEO/NE) was prepared by high-pressure homogenization. FT-IR and encapsulation efficiency analysis indicated that LEO was effectively encapsulated in the nanoemulsion. The results of zeta potential changes after 35 d storage indicated that LEO/NE exhibits good stability at room temperature. The effect of LEO/NE on the main soft rot pathogens of kiwifruit Phomopsis sp. was investigated, and the results showed that LEO/NE significantly inhibited spore germination and mycelia growth of Phomopsis sp. by promoting ROS accumulation, intracellular antioxidant enzyme activities, and cell apoptosis. The preservation experiment was carried out by inoculating Phomopsis sp. spores into fresh kiwifruit, and the LEO/NE effectively inhibited soft rot development in kiwifruit in a LEO dose dependent manner. LEO/NE with 1% LEO loading amount has a good effect on preventing postharvest decay of kiwifruit caused by Phomopsis sp.

Density functional theory study of active sites on nitrogen-doped graphene for oxygen reduction reaction.

Oxygen reduction reaction (ORR) remains challenging due to its complexity and slow kinetics. In particular, Pt-based catalysts which possess outstanding ORR activity are limited in application with high cost and ease of poisoning. In recent years, nitrogen-doped graphene has been widely studied as a potential ORR catalyst for replacing Pt. However, the vague understanding of the reaction mechanism and active sites limits the potential ORR activity of nitrogen-doped graphene materials. Herein, density functional theory is used to study the reaction mechanism and active sites of nitrogen-doped graphene for ORR at the atomic level, focusing on explaining the important role of nitrogen species on ORR. The results reveal that graphitic N (GrN) doping is beneficial to improve the ORR performance of graphene, and dual-GrN-doped graphene can demonstrate the highest catalytic properties with the lowest barriers of ORR. These results provide a theoretical guide for designing catalysts with ideal ORR property, which puts forward a new approach to conceive brilliant catalysts related to energy conversion and environmental catalysis.

Enhanced heterogenous hydration of SO2 through immobilization of pyridinic-N on carbon materials.

Carbon materials doped with nitrogen have long been used for SO2 removal from flue gases for the benefits of the environment. The role of water is generally regarded as hydration of SO3 which is formed through the oxidization of SO2. However, the hydration of SO2, especially on the surface of N-doped carbon materials, was almost ignored. In this study, the hydration of SO2 was investigated in detail on the pyridinic nitrogen (PyN)-doped graphene (GP) surfaces. It is found that, compared with the homogeneous hydration of SO2 assisted with NH3 in gas phase, the heterogeneous hydration is much more thermodynamically and kinetically favourable. Specifically, when a single H2O molecule is involved, the energy barrier for SO2 hydration is as low as 0.15 eV, with 0.59 eV released, indicating the hydration of SO2 can occur at rather low water concentration and temperature. Thermodynamic integration molecular dynamics results show the feasibility of the hydrogenated substrate recovery and the immobilized N acting as a catalytic site for SO2 hydration. Our findings show that the heterogeneous hydration of SO2 should be universal and potentially uncover the puzzling reaction mechanism for SO2 catalytic oxidation at low temperature by N-doped carbon materials.