Boosting Electrocatalytic Ammonia Synthesis of Bio-Inspired Porous Mo-Doped Hematite via Nitrogen Activation.

Electrochemical N2 reduction reaction (NRR) emerges as a highly attractive alternative to the Haber-Bosch process for producing ammonia (NH3) under ambient circumstances. Currently, this technology still faces tremendous challenges due to the low ammonia production rate and low Faradaic efficiency, urgently prompting researchers to explore highly efficient electrocatalysts. Inspired by the Fe-Mo cofactor in nitrogenase, we report Mo-doped hematite (Fe2O3) porous nanospheres containing Fe-O-Mo subunits for enhanced activity and selectivity in the electrochemical reduction from N2 to NH3. Mo-doping induces the morphology change from a solid sphere to a porous sphere and enriches lattice defects, creating more active sites. It also regulates the electronic structures of Fe2O3 to accelerate charge transfer and enhance the intrinsic activity. As a consequence, Mo-doped Fe2O3 achieves effective N2 fixation with a high ammonia production rate of 21.3 ± 1.1 µg h-1 mgcat.-1 as well as a prominent Faradaic efficiency (FE) of 11.2 ± 0.6%, superior to the undoped Fe2O3 and other iron oxide catalysts. Density functional theory (DFT) calculations further unravel that the Mo-doping in Fe2O3 (110) narrows the band gap, promotes the N2 activation on the Mo site with an elongated N≡N bond length of 1.132 Å in the end-on configuration, and optimizes an associative distal pathway with a decreased energy barrier. Our results may pave the way toward enhancing the electrocatalytic NRR performance of iron-based materials by atomic-scale heteroatom doping.

[Drought-resistance evaluation of marigold cultivars based on multiple statistics analysis].

By the methods of principal component analysis, subordinate function, and cluster analysis, a comprehensive evaluation was conducted on the drought-resistance of 16 physiological indices of nine marigold cultivars. Under drought stress, the 16 physiological indices had different responses, among which, free proline (Pro), H2O2, and ascorbate peroxidase (APX) showed the greatest sensitivity. There existed significant correlations in the drought-resistance coefficients of parts of the physiological indices. Four principal factors presented 88.6% of the information of the 16 indices, and the cultivars 'Janie' and 'Gate gold', 'Bonanzn', 'Janie', and 'Chokdee' had the strongest drought-resistance for the 4 principal factors, respectively. The comprehensive evaluation value of the drought-resistance of the 9 cultivars was in the order of 'Janie' > 'Gate gold' > 'Bonanza' > 'Chokdee' > 'Giant' > 'Great hero' > 'Little hero' > 'Durango' > 'Discovery'. The 9 cultivars could be clustered into 3 groups, and 'Gate gold', 'Janie', 'Bonanza' and 'Chokdee' belonged to the drought-resistance group.