Mn3 O4 /N-Doped Graphite Catalysts from Wastewater for the Degradation of Methylene Blue.

The accelerating research interest in graphene involving the use of Hummers method has generated non-negligible amount of wastewater containing residual graphite as well as Mn2+ . In this paper, we report the first example of using this wastewater as precursor to prepare Mn3 O4 /N-doped graphite (NG) composites through a facile solvothermal process. The mass fraction of Mn3 O4 in the composites was manipulated by adding various amounts of extra Mn2+ . The conversion of Mn2+ to Mn3 O4 nanoparticles and the N atoms doping were achieved by adding hydrazine hydrate and ammonia into the system. The as-obtained Mn3 O4 /NG composites were well characterized by SEM, TEM, EDS, Raman, XPS, TGA, XRD and N2 adsorption-desorption experiments and showed excellent catalytic performances as well as stability in the degradation of a model organic pollutant methylene blue (MB). Theoretical simulation was also carried out to illustrate the structural features of the Mn3 O4 /NG composite. This work presents a novel idea of designing functional materials from waste precursors.

N-Doped Carbon Nanofibrous Network Derived from Bacterial Cellulose for the Loading of Pt Nanoparticles for Methanol Oxidation Reaction.

The large-scale, low-cost preparation of Pt-based catalysts with high activity and durability for the methanol oxidation reaction is still challenging. The key to achieving this aim is finding suitable supporting materials. In this paper, N-doped carbon nanofibrous networks are prepared by annealing a gel containing two inexpensive and ecofriendly precursors, that is, bacterial cellulose and urea, for the loading of Pt nanoparticles. An undoped analogue is also prepared for comparison. Meanwhile, the effect of the annealing temperature on the performance of the catalysts is evaluated. The results show that the N doping and higher annealing temperature can improve the electron conductivity of the catalyst and provide more active sites for the loading of ultrafine Pt nanoparticles with a narrow size distribution. The best catalyst exhibits a remarkably high electrocatalytic activity (627 mA mg-1 ), excellent poison tolerance, and high durability. This work demonstrates an ideal Pt supporting material for the methanol oxidation reaction.

Free-standing SnS/carbonized cellulose film as durable anode for lithium-ion batteries.

Metal sulfides have recently attracted broad attention for lithium-ion batteries (LIB) owing to their high theoretical capacity and long lifetime. However, the inferior structural integrity and low electron conductivity of metal sulfides limit their practical applications. A feasible strategy is to distribute these materials in conductive carbonaceous substrates with shapeable morphology. Here we report the design of free-standing films of tin sulfide (SnS) nanosheets distributed uniformly on carbonized bacterial cellulose (CBC) nanofibers. The SnS/CBC composites possess three dimensional interconnected nanostructures, which is crucial for the high conductivity and high lithium storage capacity. LIB using SnS/CBC as anode exhibits a reversible capacity of 872 mA h g-1 at 100 mA g-1 after 100 cycles, and the capacity remains as high as 527 mA h g-1 at 2000 mA g-1 after 1000 cycles. The free-standing sulfide-based nanocomposites with unique nanostructure composition and flexibility could be utilized as promising electrode materials for future LIB systems.

Reconstruction of a Genome-scale Metabolic Network of Komagataeibacter nataicola RZS01 for Cellulose Production.

Bacterial cellulose (BC) is widely used in industries owing to its high purity and strength. Although Komagataeibacter nataicola is a representative species for BC production, its intracellular metabolism leading to BC secretion is unclear. In the present study, a genome-scale metabolic network of cellulose-producing K. nataicola strain RZS01 was reconstructed to understand its metabolic behavior. This model iHZ771 comprised 771 genes, 2035 metabolites, and 2014 reactions. Constraint-based analysis was used to characterize and evaluate the critical intracellular pathways. The analysis revealed that a total of 71 and 30 genes are necessary for cellular growth in a minimal medium and complex medium, respectively. Glycerol was identified as the optimal carbon source for the highest BC production. The minimization of metabolic adjustment algorithm identified 8 genes as potential targets for over-production of BC. Overall, model iHZ771 proved to be a useful platform for understanding the physiology and BC production of K. nataicola.

Complete genome sequence of the cellulose-producing strain Komagataeibacter nataicola RZS01.

Komagataeibacter nataicola is an acetic acid bacterium (AAB) that can produce abundant bacterial cellulose and tolerate high concentrations of acetic acid. To globally understand its fermentation characteristics, we present a high-quality complete genome sequence of K. nataicola RZS01. The genome consists of a 3,485,191-bp chromosome and 6 plasmids, which encode 3,514 proteins and bear three cellulose synthase operons. Phylogenetic analysis at the genome level provides convincing evidence of the evolutionary position of K. nataicola with respect to related taxa. Genomic comparisons with other AAB revealed that RZS01 shares 36.1%~75.1% of sequence similarity with other AAB. The sequence data was also used for metabolic analysis of biotechnological substrates. Analysis of the resistance to acetic acid at the genomic level indicated a synergistic mechanism responsible for acetic acid tolerance. The genomic data provide a viable platform that can be used to understand and manipulate the phenotype of K. nataicola RZS01 to further improve bacterial cellulose production.