Reviewing perovskite oxide sites influence on electrocatalytic reactions for high energy density devices

Batteries,fuel cells,and supercapacitors are electrochemical devices already on the market and still need a boost in kinetics to match the high energy density demand of applications.Perovskites have attracted the scientific community's attention in the last decade due to their electrocatalytic activity,chemical and structural properties,tunability,low cost,and scalability.Efforts have been made to understand the active sites and the operational mechanisms in perovskite oxides to shape them as an electrocatalyst in advanced energy devices.Understanding the role of perovskites is the key to engineering more controlled and efficient electrocatalysts via chemical synthesis,and there is still much to do.This review highlights the use of perovskites in different energy storage and conversion systems.The A,B,and A&B doping-site effects are analyzed to understand the opportunities and challenges related to this class of materials.In addition,the synthesis methods and the properties related to the doping site are described and summarized.

Solution chemistry back‐contact FTO/hematite interface engineering for efficient photocatalytic water oxidation

This work describes a simple yet powerful scalable solution chemistry strategy to create back‐contact rich interfaces between substrates such as commercial transparent conducting fluorine‐doped tin oxide coated glass(FTO)and photoactive thin films such as hematite for low‐cost water oxidation reaction.High‐resolution electron microscopy(SEM,TEM,STEM),atomic force microscopy(AFM),elemental chemical mapping(EELS,EDS)and photoelectrochemical(PEC)investigations reveal that the mechanical stress,lattice mismatch,electron energy barrier,and voids between FTO and hematite at the back‐contact interface as well as short‐circuit and detrimental reaction between FTO and the electrolyte can be alleviated by engineering the chemical composition of the precursor solutions,thus increasing the overall efficiency of these low‐cost photoanodes for water oxidation reaction for a clean and sustainable generation of hydrogen from PEC water‐splitting.These findings are of significant importance to improve the charge collection efficiency by minimizing electron‐hole recombination observed at back‐contact interfaces and grain boundaries in mesoporous electrodes,thus improving the overall efficiency and scalability of low‐cost PEC water splitting devices.

Nanostructural Evolution of Sugarcane Rind and Pith Submitted to Hydrothermal Pretreatments

Lignocellulose conversion into cellulosic ethanol and coproducts starts with a pretreatment step.Most current industrial plants of cellulosic ethanol use thermochemical pretreatments under hydrothermal conditions,with or without addition of acid catalyst.Such pretreatments modify biomass chemistry and morphology,particularly at the nanoscale.In this work,we use X-ray diffraction,dynamic vapor sorption and calorimetric thermoporometry to investigate the biomass nanostructural changes promoted by hydrothermal conditions.We compare and differentiate the rind and pith fractions of sugarcane stalks in order to contribute to the understanding of rind-pith contrasting recalcitrance.Moreover,for both cane fractions our results point consistently to cellulose co-crystallization,lignin aggregation,and opening of nanoscale pores as the main nanostructural phenomena occurring during hydrothermal treatments.

Microbiota modification by probiotic supplementation reduces colitis associated colon cancer in mice

AIM To investigate the effect of probiotic supplementation during the development of an experimental model of colitis associated colon cancer(CAC). METHODS C57 BL/6 mice received an intraperitoneal injection of azoxymethane(10 mg/kg), followed by three cycles of sodium dextran sulphate diluted in water(5% w/v). Probiotic group received daily a mixture of Lactobacillus acidophilus, Lactobacil us rhamnosus and Bifidobacterium bifidum. Microbiota composition was assessed by 16 Sr RNA Illumina Hi Seq sequencing. Colon samples were collected for histological analysis. Tumor cytokines was assessed by Real Time-PCR(Polymerase Chain Reaction); and serum cytokines by Multiplex assay. All tests were two-sided. The level of significance was set at P < 0.05. Graphs were generated and statistical analysis performed using the software Graph Pad Prism 5.0. The project was approved by the institutional review board committee. RESULTS At day 60 after azoxymethane injection, the mean number of tumours in the probiotic group was 40% lower than that in the control group, and the probiotic group exhibited tumours of smaller size(< 2 mm)(P < 0.05). There was no difference in richness and diversity between groups. However, there was a significant difference in beta diversity in the multidimensional scaling analysis. The abundance of the genera Lactobacillus, Bifidobacterium, Allobaculum, Clostridium XI and Clostridium XVⅢ increased in the probiotic group(P < 0.05). The microbial change was accompanied by reduced colitis, demonstrated by a 46% reduction in the colon inflammatory index; reduced expression of the serum chemokines RANTES and Eotaxin; decreased p-IKK and TNF-α and increased IL-10 expression in the colon. CONCLUSION Our results suggest a potential chemopreventive effect of probiotic on CAC. Probiotic supplementation changes microbiota structure and regulates the inflammatory response, reducing colitis and preventing CAC.

CeO_(2)-Nb_(2)O_(5)photocatalysts for degradation of organic pollutants in water

The photocatalytic properties of CeO2-Nb2O5 photocatalysts in heterogeneous photocatalysis(under ultraviolet and visible radiation)and in Fenton-like process were reported.Methylene blue dye(MB)and phenol(Ph)were used as models of pollutant molecules for these reactions,and the photocatalysts were characterized by X-ray diffraction(XRD),diffuse reflectance spectroscopy(DRS),scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDX)and thermally stimulated luminescence(TL).The results indicated that the addition of CeO2(0.3 wt%,1.0 wt%and 2.0 wt%)to Nb2O5 sensitized the resultant materials,increasing light absorption in the visible region.However,there is a suitable formulation of CeO2-Nb2O5 photocatalysts to improve each photocatalytic process.In heterogeneous photocatalysis,the addition of small CeO2 quantities to Nb2O5 was enough to improve the photocatalytic activity of CeO2-Nb2O5 photocatalysts(The best composition reported was CeO20.3 wt%.).The effectiveness of the catalyst was explained by the decrease in the number of trapping and luminescence centers in the conduction band of the material after the addition of CeO2 to Nb2O5,but a large amount of CeO2 decreased the number of trapping,luminescent and active centers to a large extent.Contrarily,in a Fenton-like process,the addition of CeO2 to Nb2O5 was favorable in all the proportions studied.(The best composition was 2.0 wt%CeO2.)In this case,the effectiveness was explained by the influence of the adsorption process(adsorption-triggered process),and the interactions between H2 O2 and Ce3+of the CeO2 in each photocatalyst thus formed surface peroxide species O22-,which induced the removal of the organic molecules under visible light.

Utilization of Acai Berry Residual Biomass for Extraction of Lignocellulosic Byproducts

According to the National Company of Supplying(CONAB)in 2017 alone,the national production of acai pulp reached 219855 t,equating to 180 million dollar(USD).Almost 85%of the weight of fruit is constituted by residual biomass,even though researches have highlighted important applications for this biomass,most of it is discarded as organic waste.Thus,it is relevant to envisage in-depth studies about how to use these residues,particularly regarding the environmental impact of its target destination.Nanocrystalline cellulose(CNC)and lignin are organic derivatives obtained through the physical-chemical treatment of lignocellulosic biomass.Both are abundant and currently considered as biopolymers because of their structural characteristics and their diverse applications in food and the medical field.This work presents the mass yields achieved and the physical-chemical characteristics of the lignocellulosic derivatives extracted from the fiber of the acai berry.A statistical design was used to define the influence of process variables as temperature,reaction time and fiber size on the yield of these byproducts.A maximum yield close to 64%of type I CNC,with 45%of crystallinity degree was achieved at the minimum condition of temperature and fiber size.Additionally,through rheological analysis,it was possible to predict the nanocrystal aspect ratios,ranging from 71 to 125.The extracted lignin was rich in methoxy groups,p-coumaryl alcohol and p-coumaric acid,and its structural unit’s low state of aggregation can be an indication of low molecular weight,which envisions an appropriate use for this lignin to produce commodity chemicals.