Cao Renfei,Cui Yangfeng,Huang Gang,Liu Wanqiang,Liu Jianwei,Zhang Xinbo
Li-O 2 batteries with extremely high specific energy density have been regarded as a kind of promising successor to current Li-ion batteries. However, the high charge overpotential for the decomposition of Li 2 O 2 discharge product reduces the energy efficiency and triggers a series of side reactions that cause the Li-O 2 batteries to have a limited lifetime. Herein, Co-doped C 3 N 4 (Co-C 3 N 4 ) photocatalysts were designed by an in situ thermal evaporation method to take advantage of the photo-assisted charging technology to conquer the shortcomings of Li-O 2 batteries encountered in the charge process. Different from the commonly used photocatalysts, the Co-C 3 N 4 photocatalysts perform well no matter with and without illumination, owing to the Co doping induced conductivity and electrocatalytic ability enhancement. This makes the Co-C 3 N 4 reduce the charge and discharge overpotentials and improve the cycling performance of Li-O 2 batteries (from 20 to 106 cycles) without illumination. While introducing illumination, the performance can be further improved: Charge voltage reduces to 3.3 V, and the energy efficiency increases to 84.84%, indicating that the Co-C 3 N 4 could behave as a suitable photocathode for Li-O 2 batteries. Besides, the low charge voltage and the continuous illumination together weaken the corrosion of the Li anode, making the long-term high-efficiency operation of Li-O 2 batteries no longer just extravagant hope.
The Co–C3N4/BiPO4 photocatalyst is facilely synthesized for application in photocatalytic water splitting. The physical and chemical properties of Co–C3N4/BiPO4 are studied by a wide range of characterization methods. The Co–CN/BP photocatalyst shows good photocatalytic activity for H2 evolution by water splitting without using a noble metal. The Co–C3N4/BiPO4 composite with 5 wt% Co–C3N4 loading exhibits a superior photocatalytic H2 evolution rate of 23.9 μmol h−1 g−1. The remarkable enhancement of the photocatalytic H2 evolution activity of Co–C3N4/BiPO4 composites is mainly ascribed to the effective charge transfer and separation of the electron–hole pairs by the lattice-matched heterojunction structure. This work extends opportunities for the design of non-noble metal photocatalysts with efficient photocatalytic water splitting.
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