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Developing cost-effective electrocatalysts for oxygen reduction reaction (ORR) is of great importance to improve the performance of metal–air batteries. Herein, a CoNi alloy encapsulated in an N-doped carbon framework (CoNi@NC) with a high saturation magnetization (89.1 emu g–1) is prepared by nanoalloying, and an external magnetic field is employed to directly enhance the ORR performance of CoNi@NC. The electronic structure of CoNi@NC is greatly optimized by electron cloud redistribution and spin-state adjustment, leading to Pt/C-comparable ORR performance in an alkaline electrolyte (the onset potential of 0.98 V and half-wave potential of 0.86 V in 0.1 M KOH). Furthermore, the CoNi@NC-based Al–air battery with magnet delivers a larger power density of 161.27 mW cm–2 and exhibits better durability compared with those with Pt/C. This work provides a promising approach to using magnetic induction to enhance oxygen reduction activity for metal–air batteries.

Oxygen reduction electrocatalysts play important roles in metal–air batteries. Herein, Fe3C-TiN heterostructural quantum dots loaded on carbon nanotubes (FCTN@CNTs) are prepared as electrocatalysts for the oxygen reduction reaction (ORR) through a one-pot pyrolysis. The Fe3C-TiN quantum dots with a diameter of 2–5 nm show the unique characteristic of heterostructural interface. The as-prepared FCTN@CNTs display Pt/C comparable ORR performance (E onset 1.06 and E 1/2 0.95 V) in alkaline medium, which is ascribed to the heterostructural interface between TiN and Fe3C. Furthermore, the Al–air batteries with the FCTN@CNT catalyst display superior discharge performance, demonstrating good feasibility for practical application. This work provides an effective new method to synthesize affordable and efficient oxygen reduction reaction catalysts.

The rational design of non-noble metal-based electrocatalysts for an efficient oxygen reduction reaction (ORR) is an important research topic to promote the advancement of aluminum−air batteries. In this work, heterostructural Co/MnO nanoparticles encapsulated in a N-doped carbon electrocatalyst were prepared via one-step pyrolysis utilizing different reduction potentials of Co and Mn ions, and the heterointerface between the two phases was confirmed. The prepared catalyst displays Pt/C competitive ORR performance because of the interfacial synergy of a Co/MnO Mott−Schottky (M−S) heterostructure, which leads to boosted conductivity, formation of an M−S barrier, and a reduced oxygen reduction energy barrier for excited electrons. Furthermore, the Co/MnO-based aluminum−air battery displays good discharge performance, demonstrating good feasibility for practical application.

The vegetation coverage on the Loess Plateau (LP) of China has clearly increased since the implementation of the Grain for Green Project in 1999, but there is a debate about whether the improved greenness was achieved at the expense of the balance between the supply and demand of water resources. Therefore, developing reliable indicators to evaluate the water availability is a prerequisite for maintaining ecological sustainability and ensuring the persistence of vegetation restoration. This study was designed to evaluate water availability on the LP during 2000–2015, using the evaporative stress index (ESI) derived from a remote sensing dataset. The relative dependences of the ESI on climatic and biological factors (including temperature, precipitation and land cover change) were also analyzed. The results showed that the leaf area index (LAI) in most regions of the LP showed a significant increasing trend (p < 0.05), and larger gradients of increase were mainly detected in the central and eastern parts of the LP. The evapotranspiration also exhibited an increasing trend in the central and eastern parts of the LP, with a gradient greater than 10 mm/year. However, almost the whole LP exhibited a decreased ESI from 2000 to 2015, and the largest decrease occurred on the central and eastern LP, indicating a wetting trend. The soil moisture storage in the 0–289-cm soil profiles showed an increasing trend in the central and eastern LP, and the area with an upward trend enlarged with the soil depth. Further analysis revealed that the decreased ESI on the central and eastern LP mainly depended on the increase in the LAI compared with climatic influences. This work not only demonstrated that the ESI was a useful indicator for understanding the water availability in natural and managed ecosystems under climate change but also indicated that vegetation restoration might have a positive effect on water conservation on the central LP.

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