Ultrathin cobalt-based nanosheets containing surface oxygen promoted near-complete nitrate removal.

Electrocatalytic nitrate removal offers a sustainable approach to alleviate nitrate pollution and to boost the anthropogenic nitrogen cycle, but it still suffers from limited removal efficiency at high rates, especially at low levels of nitrate. Herein, we report the near-complete removal of low-level nitrate (10-200 ppm) within 2 h using ultrathin cobalt-based nanosheets (CoNS) containing surface oxygen, which was fabricated from in-situ electrochemical reconstruction of conventional nanosheets. The average nitrate removal of 99.7 % with ammonia selectivity of 98.2 % in 9 cyclic runs ranked in the best of reported catalysts. Powered by a solar cell under the winter sun, the full-cell nitrate electrolysis system, equipped with ultrathin CoNS, achieved 100 % nitrogen gas selectivity and 99.6 % total nitrogen removal. The in-situ Fourier Transform Infrared included experiments and theoretical computations revealed that in-situ electrochemical reconstruction not only increased electrochemical active surface area but also constructed surface oxygen in active sites, leading to enhanced stabilization of nitrate adsorption in a symmetry breaking configuration and charge transfer, contributing to near-complete nitrate removal on ultrathin CoNS. This work provides a strategy to design ultrathin nanocatalysts for nitrate removal.

Activating nickel foam with trace titanium oxide for enhanced water oxidation.

Nickel-based electrocatalysts for water oxidation suffer from low activity and poor stability. In this work, 0.015 mg cm-2 TiO2 nanosheets anchored on Ni foam addressed these problems after electrochemical activation. In situ investigations, including Raman spectra, corroborated the enhanced generation of highly active Ni(III)-O-O species on Ni foam in the presence of trace TiO2.

The early response expression profiles of miRNA-mRNA in farmed yellow catfish (Pelteobagrus fulvidraco) challenged with Edwardsiella tarda infection.

Edwardsiella tarda, the bacterial pathogen that causes ascites disease and red-head disease, poses a serious threat to yellow catfish (Pelteobagrus fulvidraco) aquaculture. In this study, the spleens of E. tarda-infected and non-infected yellow catfish were sequenced to obtain the microRNA (miRNA) and mRNA expression profiles. We obtained 657 differentially expressed (DE) miRNAs and 6867 DE mRNAs between two groups and annotated them using the KEGG database. In addition, the 43 negatively correlated miRNA-mRNA pairs were identified using integrated miRNA-mRNA analysis, which including immune-related miRNAs and target genes such as miR-144, miR-1260, miR-1388, miR-33, miR-338, miR-181b, miR-34c, miR-135 and CLEC4E, LITR, PIKfyve, NCF4, IL-12ß, IP6K2, TNFRSF9, IL-4Rα, IRF2, Mx2. We verified 8 DE miRNAs pairs and 10 DE mRNAs by quantitative real-time PCR. Finally, the CLEC4E and Mx2 mRNAs were selected for further verification using in situ hybridization. Together, our results provide valuable information for further analyses of the mechanisms of yellow catfish defense against E. tarda infection.

Reduced graphene oxide supported palladium nanoparticles via photoassisted citrate reduction for enhanced electrocatalytic activities.

Reduced graphene oxide (rGO) supported palladium nanoparticles (Pd NPs) with a size of ∼3 nm were synthesized using one-pot photoassisted citrate reduction. This synthetic approach allows for the formation and assembly of Pd NPs onto the rGO surface with a desired size and can be readily used for other metal NP preparation. The prepared rGO-Pd exhibited 5.2 times higher mass activity for ethanol oxidation reaction than the commercial platinum/carbon (Pt/C). In the oxygen reduction reaction tests, rGO-Pd exhibited comparable activity compared with Pt/C and maintained its high performance after 4000 cycles of potential sweep. These results demonstrate that our synthetic approach is effective for preparing graphene-supported metal NPs with excellent activity and stability in ethanol oxidation and oxygen reduction reactions.

Phenothiazine derivative-accelerated microbial extracellular electron transfer in bioelectrochemical system.

In bioelectrochemical system (BES) the extracellular electron transfer (EET) from bacteria to anode electrode is recognized as a crucial step that governs the anodic reaction efficiency. Here, we report a novel approach to substantially enhance the microbial EET by immobilization of a small active phenothiazine derivative, methylene blue, on electrode surface. A comparison of the currents generated by Shewanella oneidensis MR-1 and its mutants as well as the electrochemical analytical results reveal that the accelerated EET was attributed to enhanced interactions between the bacterial outer-membrane cytochromes and the immobilized methylene blue. A further investigation into the process using in situ Raman spectro-electrochemical method coupled with density functional theory calculations demonstrates that the electron shuttling was achieved through the change of the molecule conformation of phenothiazine in the redox process. These results offer useful information for engineering BES.

Graphene oxide nanoribbons greatly enhance extracellular electron transfer in bio-electrochemical systems.

Bridging microbes and electrode to facilitate the extracellular electron transfer (EET) is crucial for bio-electrochemical systems (BESs). Here, a significant enhancement of the EET process was achieved by biomimetically fabricating a network structure of graphene oxide nanoribbons (GONRs) on the electrode. This strategy is universal to enhance the adaptability of GONRs at the bio-nano interface to develop new bioelectronic devices.