Direct chemical synthesis from methane and air under ambient conditions is attractive yet challenging. Low-valent organometallic compounds are known to activate methane, but their electron-rich nature seems incompatible with O2 and prevents catalytic air oxidation. We report selective oxidation of methane to methanol with an O2-sensitive metalloradical as the catalyst and air as the oxidant at room temperature and ambient pressure. The incompatibility between C–H activation and O2 oxidation is reconciled by electrochemistry and nanomaterials, with which a concentration gradient of O2 within the nanowire array spatially segregated incompatible steps in the catalytic cycle. An unexpected 220 000-fold increase of the apparent reaction rate constants within the nanowire array leads to a turnover number up to 52 000 within 24 h. The synergy between nanomaterials and organometallic chemistry warrants a new catalytic route for CH4 functionalization.

The collective motion of Bacillus subtilis in the presence of a photosensitizer is disrupted by reactive oxygen species when exposed to light of sufficient dosages and is partially recovered when light irradiation is suspended. The transition from a highly collective to a more random motion is modeled using an improved self-propelled model with alignment rule. The increment in noise level describes the enhanced uncertainty in the motion of swarming bacteria under stress as observed experimentally.

No abstract

Root nodules are agricultural-important symbiotic plant-microbe composites in which microorganisms receive energy from plants and reduce dinitrogen (N 2 ) into fertilizers. Mimicking root nodules using artificial devices can enable renewable energy-driven fertilizer production. This task is challenging due to the necessity of a microscopic dioxygen (O 2 ) concentration gradient, which reconciles anaerobic N 2 fixation with O 2 -rich atmosphere. Here we report our designed electricity-powered biological|inorganic hybrid system that possesses the function of root nodules. We construct silicon-based microwire array electrodes and replicate the O 2 gradient of root nodules in the array. The wire array compatibly accommodates N 2 -fixing symbiotic bacteria, which receive energy and reducing equivalents from inorganic catalysts on microwires, and fix N 2 in the air into biomass and free ammonia. A N 2 reduction rate up to 6.5 mg N 2 per gram dry biomass per hour is observed in the device, about two orders of magnitude higher than the natural counterparts.

will benefit from a model that includes both the electrochemical NRR and HER kinetics.We aim to contribute a model for electrochemical N 2 reduction with the following factors taken into consideration. As both NRR and HER are proton-coupled electron transfer (PCET) reactions that consumes protons, [7,16,17] the underlying HER and NRR mechanisms are indeed intertwined. A microkinetic approach on the electrode should be considered and the model should not only manage the fate of reducing electrons but also tackle the protonation of reduced species. As N 2 exhibits extremely weak Brønsted basicity, we posit that the initial NRR steps include an electron transfer (ET) followed by a proton transfer (PT) (Figure 1A). On the other hand, the mechanism of HER should include a Volmer step followed by a Tafel or Heyrovský step ( Figure 1B). [18][19][20] Additionally, we are reluctant to preemptively define the rate-determining steps (RDSs) in both NRR and HER, although it is commonly argued that at least some NRR catalysts undergo a rate-determining ET process. [7,[21][22][23] Such a practice may help to illustrate the importance of proton availability on the reaction selectivity, which has been evident in the case of electrochemical CO 2 reduction. [24] Last, the developed microkinetic model should include electrode morphology and be capable to provide guidance for the development of nano-or microstructured electrodes. As N 2 exhibits limited solubility and there may be limited sources of proton in electrolyte, the NRR selectivity could be modulated by the mass transport of redox species in nano-or microstructured electrodes, analogous to the reports in electrochemical CO 2 reduction. [25,26] Here we report a model of electrochemical N 2 reduction that satisfies the abovementioned requirements. As a proofof-principle, the model was numerically simulated with finite element method under an aqueous electrolyte of 0.1 m nonoxidizing strong acid. A database of results was constructed, by simulating the model under a library of different materials' NRR and HER catalytic activities represented by the corresponding exchange current densities. The numerical simulations yield results consistent with expectations from experimental reports. [23,27] The results also imply that the PT step in NRR process can be dominant under certain combinations of NRR and HER exchange current densities and mass transport conditions, although in most cases the ET step is the One major challenge of electrocatalytic dinitrogen (N 2 ) reduction is the competition between nitrogen reduction reaction (NRR) and hydrogen evolution reaction (HER). While experimental development of selective NRR catalysts is indispensable, the aim is to derive insights of catalyst design by developing a model that includes both the kinetics of competing reactions on the electrode and the mass transport of reactants in solution. The developed microkinetic model is reported here and it is applied to evaluate NRR selectivity on planar and microstructured electrodes. As a proof-of...

Neural networks, trained on data generated by a microkinetic model and finite-element simulations, expand explorable parameter space by significantly accelerating the predictions of electrocatalytic performance. In addition to modeling electrode reactivity, we use micro/nanowire arrays as a well-defined, easily tuned, and experimentally relevant exemplary morphology for electrochemical nitrogen fixation. This model system provides the data necessary for training neural networks which are subsequently exploited for electrocatalytic material morphology optimizations and explorations into the influence of geometry on nitrogen fixation electrodes, feats untenable without large-scale simulations, on both a global and a local basis.

Deep eutectic solvents (DESs) have attracted extensive research for their potential applications as leaching solvent to recycle valuable metal elements from spent lithium ion batteries (LIBs). Despite various advantages like being economical and green, the full potential of conventional binary DES has not yet been harnessed because of the kinetics during leaching. Herein, we consider the fundamental rate-determining-step (RDS) in conventional binary DES and attempt to design ternary DES, within which the chemical reaction kinetics and diffusion kinetics can be regulated to maximize the overall leaching rate. As a proof of concept, we show that the ternary choline chloride/succinic acid/ethylene glycol (ChCl/SA/EG) type ternary DES can completely dissolve LCO powder at 140 °C in 16 h. By systematically studying the leaching process at various conditions, the energy barrier during leaching can be calculated to be 11.77 kJ/mol. Furthermore, we demonstrate that the extraction of the cobalt ions from the leaching solution can be directly achieved by adding oxalic ions without neutralizing the solution. The precipitate can be used to regenerate LCO with high purity. The recycled materials show comparable electrochemical performance with commercial LCO. Our design strategy of ternary DES with regulated RDS is expected to have both scientific and technological significance in the field of hydrometallurgical recycling of LIBs.

An intelligent drug release system that is triggered into action upon sensing the motion of swarmer P. mirabilis is introduced. The rational design of the drug release system focuses on a pNIPAAm-co-pAEMA copolymer that prevents drug leakage in a tobramycin-loaded mesoporous silica particle by covering its surface via electrostatic attraction. The copolymer chains are also conjugated to peptide ligands YVLWKRKRKFCFI-NH2 that display affinity to Gram-negative bacteria. When swarmer P. mirabilis cells approach and come in contact with the particle, the copolymer-YVLWKRKRKFCFI-NH2 binds to the lipopolysaccharides on the outer membrane of motile P. mirabilis and are stripped off the particle surface when the cells move away; hence releasing tobramycin into the swarmer colony and inhibiting its expansion. The release mechanism is termed Motion-Induced Mechanical Stripping (MIMS). For swarmer B. subtilis, the removal of copolymers from particle surfaces via MIMS is not apparent due to poor adherence between bacteria and copolymer-YVLWKRKRKFCFI-NH2 system.