Polynary single‐atom structures can combine the advantages of homogeneous and heterogeneous catalysts while providing synergistic functions based on different molecules and their interfaces. However, the fabrication and identification of such an active‐site prototype remain elusive. Here we report isolated diatomic Ni‐Fe sites anchored on nitrogenated carbon as an efficient electrocatalyst for CO2 reduction. The catalyst exhibits high selectivity with CO Faradaic efficiency above 90 % over a wide potential range from −0.5 to −0.9 V (98 % at −0.7 V), and robust durability, retaining 99 % of its initial selectivity after 30 hours of electrolysis. Density functional theory studies reveal that the neighboring Ni‐Fe centers not only function in synergy to decrease the reaction barrier for the formation of COOH* and desorption of CO, but also undergo distinct structural evolution into a CO‐adsorbed moiety upon CO2 uptake.

Titanium dioxide (TiO2) is a prototype, water-splitting (photo)catalyst, but its performance is limited by the large overpotential for the oxygen evolution reaction (OER). We report here a first-principles density functional theory study of the chemical dynamics of the first proton-coupled electron transfer (PCET), which is considered responsible for the large OER overpotential on TiO2. We use a periodic model of the TiO2/water interface that includes a slab of anatase TiO2 and explicit water molecules, sample the solvent configurations by first principles molecular dynamics, and determine the energy profiles of the two electronic states involved in the electron transfer (ET) by hybrid functional calculations. Our results suggest that the first PCET is sequential, with the ET following the proton transfer. The ET occurs via an inner sphere process, which is facilitated by a state in which one electronic hole is shared by the two oxygen ions involved in the transfer.

The direct synthesis of TiN nanoparticles on carbon black (CB) was achieved using an mpg-C(3)N(4)/CB composite as a template. The obtained TiN/CB composites ensured improved contact between TiN and CB, functioning as an efficient cathode catalyst for oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs). The preparation procedure developed in this study is applicable for the synthesis of a variety of supported nano-nitride catalysts.

aBL has antimicrobial activity in biofilms ofA. baumannii and P. aeruginosa and is a potential therapeutic approach for biofilm-related infections.

Density functional theory (DFT) calculations with on-site Coulomb repulsion are carried out to study the relative stabilities of crystalline cobalt oxides and hydroxidesCoO, Co(OH)2, Co3O4, CoO(OH), and CoO2in electrochemical environment. Co(OH)2 is the thermodynamic ground state under reducing conditions, i.e., at voltages V < 0 relative to the standard hydrogen electrode (SHE) potential in acidic solution, whereas CoO(OH) and CoO2 are stable under oxidizing conditions, i.e., at external voltage larger than 1.23 eV vs SHE in basic solution. These results, combined with surface structure studies of the (0001) natural cleavage surface of CoO(OH), show that a CoO2 x– (x = 0–0.5) layer is present when the surface is exposed to solution under oxidizing conditions, in agreement with recent experimental findings. Study of the energetics of water oxidation at regular surface sites of CoO(OH)(0001) indicates however that water deprotonation to form a surface OH species is energetically very costly. Different active sites, e.g. steps, are thus responsible for the observed high activity of crystalline cobalt oxide for electrochemical oxygen evolution.

Transition metal nitrogen carbon based single‐atom catalysts (SACs) have exhibited superior activity and selectivity for CO2 electroreduction to CO. A favorable local nitrogen coordination environment is key to construct efficient metal‐N moieties. Here, a facile plasma‐assisted and nitrogen vacancy (NV) induced coordinative reconstruction strategy is reported for this purpose. Under continuous plasma striking, the preformed pentagon pyrrolic N‐defects around Ni sites can be transformed to a stable pyridinic N dominant Ni‐N2 coordination structure with promoted kinetics toward the CO2‐to‐CO conversion. Both the CO selectivity and productivity increase markedly after the reconstruction, reaching a high CO Faradaic efficiency of 96% at mild overpotential of 590 mV and a large CO current density of 33 mA cm‐2 at 890 mV. X‐ray adsorption spectroscopy and density functional theory (DFT) calculations reveal this defective local N environment decreases the restraint on central Ni atoms and provides enough space to facilitate the adsorption and activation of CO2 molecule, leading to a reduced energy barrier for CO2 reduction.

Polynary single-atom structures can combine the advantages of homogeneous and heterogeneous catalysts while providing synergistic functions based on different molecules and their interfaces.However,the fabrication and identification of such an active-site prototype remain elusive.Here we report isolated diatomic Ni-Fesites anchored on nitrogenated carbon as an efficient electrocatalyst for CO 2 reduction. The catalyst exhibits high selectivity with CO Faradaic efficiency above 90 %overawide potential range from À0.5 to À0.9 V(98 %at À0.7 V), and robust durability,r etaining 99 %o fi ts initial selectivity after 30 hours of electrolysis.D ensity functional theory studies reveal that the neighboring Ni-Fec enters not only function in synergy to decrease the reaction barrier for the formation of COOH* and desorption of CO,but also undergo distinct structural evolution into aC O-adsorbed moiety upon CO 2 uptake. Figure 4. a) Calculated free energy diagrams for CO 2 RR yielding CO on different catalysts.b )The catalytic mechanism on diatomic metalnitrogen site based on the optimized structures of adsorbed intermediates COOH* and CO*. c) Difference in limiting potentials for CO 2 reduction and H 2 evolution of different catalysts.

BackgroundThis proof-of-principle study examines whether postnatal, low-dose exposure to environmental chemicals modifies the composition of gut microbiome. Three chemicals that are widely used in personal care products—diethyl phthalate (DEP), methylparaben (MPB), triclosan (TCS)—and their mixture (MIX) were administered at doses comparable to human exposure to Sprague-Dawley rats from birth through adulthood. Fecal samples were collected at two time points: postnatal day (PND) 62 (adolescence) and PND 181 (adulthood). The gut microbiome was profiled by 16S ribosomal RNA gene sequencing, taxonomically assigned and assessed for diversity.ResultsMetagenomic profiling revealed that the low-dose chemical exposure resulted in significant changes in the overall bacterial composition, but in adolescent rats only. Specifically, the individual taxon relative abundance for Bacteroidetes (Prevotella) was increased while the relative abundance of Firmicutes (Bacilli) was reduced in all treated rats compared to controls. Increased abundance was observed for Elusimicrobia in DEP and MPB groups, Betaproteobacteria in MPB and MIX groups, and Deltaproteobacteria in TCS group. Surprisingly, these differences diminished by adulthood (PND 181) despite continuous exposure, suggesting that exposure to the environmental chemicals produced a more profound effect on the gut microbiome in adolescents. We also observed a small but consistent reduction in the bodyweight of exposed rats in adolescence, especially with DEP and MPB treatment (p < 0.05), which is consistent with our findings of a reduced Firmicutes/Bacteroidetes ratio at PND 62 in exposed rats.ConclusionsThis study provides initial evidence that postnatal exposure to commonly used environmental chemicals at doses comparable to human exposure is capable of modifying the gut microbiota in adolescent rats; whether these changes lead to downstream health effects requires further investigation.Electronic supplementary materialThe online version of this article (doi:10.1186/s40168-016-0173-2) contains supplementary material, which is available to authorized users.