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.

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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...