Photo-assisted lithium–oxygen (Li–O₂) batteries have been developed as a new system to reduce a large overpotential in the Li–O₂ batteries. However, constructing an optimized photocatalyst is still a challenge to achieve broad light absorption and a low recombined rate of photoexcited electrons and holes. Herein, oxygen vacancy-rich molybdenum trioxide (MoO_3−x) nanorods are employed as photocatalysts to accelerate kinetics of cathode reactions in the photo-assisted Li–O₂ batteries. Oxygen vacancies on the MoO_3−x nanorods can not only increase light-harvesting capability but also improve electrochemical activity for the cathode reactions. Under illumination, the photoexcited electrons and holes are effectively separated on the MoO_3−x nanorods. During discharging, activated O₂ is reduced to Li₂O₂ by the photoexcited electrons from the MoO_3−x nanorods. The photoexcited holes can promote the decomposition of Li₂O₂ during subsequent charging. Accordingly, the photo-assisted Li–O₂ batteries with the MoO_3−x nanorods deliver an ultralow overpotential of 0.22 V, considerable rate capability, and good reversibility. We think that this work could give a reference for the exploitation and application of the photocatalysts in the photo-assisted Li–O₂ batteries.

Motivated by the fast-developing spin dynamics in ferromagnetic/piezoelectric structures, this study attempts to manipulate magnons (spin-wave excitations) by the converse magnetoelectric (ME) coupling. Herein, electric field (E-field) tuning magnetism, especially the surface spin wave, is accomplished in Ni/0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (PMN-PT) multiferroic heterostructures. The Kerr signal (directly proportional to magnetization) changes of Ni film are observed when direct current (DC) or alternative current (AC) voltage is applied to PMN-PT substrate, where the signal can be modulated breezily even without extra magnetic field (H-field) in AC-mode measurement. Deserved to be mentioned, a surface spin wave switch of "1" (i.e., "on" ) and "0" (i.e., "off" ) has been created at room temperature upon applying an E-field. In addition, the magnetic anisotropy of heterostructures has been investigated by E-field-induced ferromagnetic resonance (FMR) shift, and a large 490 Oe shift of FMR is determined at the angle of 45° between H-field and heterostructure plane.

The sluggish reaction kinetics at the oxygen cathode is one of the important issues hindering the commercialization of the metal-air batteries. Although the noble metal can be used as the high-efficiency electrocatalyst to solve the problems to some extent, the high cost and scarcity of these noble-metal catalysts have limited their application in electrocatalysis. In this review, we discussed the mechanisms of the ORR and OER, and proposed the principles for the bifunctional electrocatalysts firstly, and then the state-of-the-art bifunctional catalysts, including carbon-based materials and transition-metal-based materials. On the basis of that, the self-supporting 3D noble-metal-free bifunctional ORR/OER catalysts were also discussed. Finally, the perspectives for the bifunctional electrocatalysts were discussed.