Centimeter-scale perovskite SrTaO2N single crystals with enhanced photoelectrochemical performance

Photoelectrochemical Lithium Extraction from Waste Batteries

The amount of global hybrid-electric and all electric vehicle has increased dramatically in just five years and reached an all-time high of over 10 million units in 2022. A good deal of waste lithium (Li)-containing batteries from dead vehicles are invaluable unconventional resources with high usage of Li. However, the recycle of Li by green approaches is extremely inefficient and rare from waste batteries, giving rise to severe environmental pollutions and huge squandering of resources. Thus, in this mini review, we briefly summarized a green and promising route-photoelectrochemical (PEC) technology for extracting the Li from the waste lithium-containing batteries. This review first focuses on the critical factors of PEC performance, including light harvesting, charge-carrier dynamics, and surface chemical reactions. Subsequently, the conventional and PEC technologies applying in the area of Li recovery processes are analyzed and discussed in depth, and the potential challenges and future perspective for rational and healthy development of PEC Li extraction are provided positively.

Growth of submillimeter SrTaO2N single crystals by an NH3-assisted SrCl2 flux method

Perovskite-type oxynitrides have recently been highlighted due to their dielectric and photocatalytic properties. Numerous studies have addressed the synthesis and characterization of their nanocrystals and ceramics. However, few research works have considered single-crystal formation in such systems due to difficulties in melt growth. In this study, we explore the crystal growth of perovskite-type oxynitride SrTaO2N by an NH3-assisted SrCl2 flux method. Submillimeter-sized single crystals with lengths of approximately 300 μm were grown at a temperature of 1200 °C for 10 h with a solute concentration of 1.5 mol%. Subsequently, the crystal growth mechanism of SrTaO2N in an SrCl2 flux was studied systematically through experiments with variable holding temperature, holding time, cooling rate, and solute concentration. Our results suggest that SrTaO2N crystal growth is induced by the evaporation of SrCl2 flux.

Narrowing the band gap and suppressing electron-hole recombination in β-Fe2O3 by chlorine doping

The effects of halogen (F, Cl, Br, I, and At) doping in the direct-band-gap β-Fe₂O₃ semiconductor on its band structures and electron-hole recombination have been investigated by density functional theory. Doping Br, I, and At in β-Fe₂O₃ leads to transformation from a direct-band-gap semiconductor to an indirect-band-gap semiconductor because their atomic radii are too large; however, F- and Cl-doped β-Fe₂O₃ remain as direct-band-gap semiconductors. Due to the deep impurity states of the F dopant, this study focuses on the effects of the Cl dopant on the band structures of β-Fe₂O₃. Two impurity levels are introduced when Cl is doped into β-Fe₂O₃, which narrows the band gap by approximately 0.3 eV. After doping Cl, the light-absorption edge of β-Fe₂O₃ redshifts from 650 to 776 nm, indicating that its theoretical solar to hydrogen efficiency for solar water splitting increases from 20.6% to 31.4%. In addition, the effective mass of the holes in halogen-doped β-Fe₂O₃ becomes significantly larger than that in undoped β-Fe₂O₃, which may suppress electron-hole recombination.