Zhen Wang,Chenteng Sun,Qian Xu,Xingli Zou,Hongwei Cheng,Xionggang Lu
Alkali and alkali earth oxides show good CO2 capture performance for carbonation, while their regeneration occurs at high temperatures, leading to a high energy penalty. When alkali oxides and alkali earth oxides combine with SiO2 to form oxysalts, the regeneration temperatures can be reduced, and the CO2 adsorption capacity is maintained. In this study, the reaction between CO2 and Li2CaSiO4, composed of stoichiometric CaO, Li2O, and SiO2, was evaluated thermodynamically by DFT. The synthesized Li2CaSiO4 with and without alkali carbonates was used as CO2 sorbents, and their CO2 adsorption performances were examined using thermal analyses. The phase and morphology of Li2CaSiO4 before and after CO2 adsorption were characterized by XRD and SEM. According to the thermodynamic evaluation and the XRD results, Li2CaSiO4 could adsorb CO2 and form CaCO3 and Li2SiO3. The thermal analyses showed that the regeneration of Li2CaSiO4 started from 575 °C, at which it was difficult to realize the CO2 diffusion through the solid CaCO3 product layer. The mixed alkali carbonates can improve the kinetics and facilitate the CO2 adsorption of Li2CaSiO4. Alkali carbonates were effective in reducing the activation energy of the reaction and CO2 diffusion at low temperatures and improving the cyclic stability because of the dispersing carbonation products.
Yi Zhang,Xihui Shan,Xulong Lv,Dongxun Chen,Shihai Miao,Weili Wang,Yanjie Liang
Discovering multimodal luminescent materials capable of being excited by diverse excitation sources and producing different wavelengths of light emission in a single material system remains a long-standing challenge. Herein, a Pr 3+ single-doped Li 2 CaSiO 4 phosphor is reported as an efficient multimodal luminescence material, which responds to convenient light sources including X-ray tube, 450 nm blue LED/laser, and white LED. Upon X-ray excitation, intense long-lasting red (>24 h) and ultraviolet-C (UVC, >12 h) persistent luminescence can be detected simultaneously, enabling a self-sustained glowing material suitable for working in both dark and bright environments. Significant enhancement of UVC afterglow is observed under the continuous photostimulation of white LED. Moreover, under the excitation of blue light, UVC upconversion luminescence is realized with the aid of unique energy levels of the Pr 3+ emitter. Besides, this material also exhibits exceptional white-to-brown photochromism performance in bright fields only in response to X-ray irradiation, accompanied by excellent bleaching and recovery capability upon thermal or blue light stimulation. The combination of persistent luminescence, photo-stimulated luminescence, upconversion luminescence and photochromism in this integrated multimodal luminescent Li 2 CaSiO 4 :Pr 3+ phosphor provides new and exciting directional solutions for multifunctional applications such as optical information storage and anti-counterfeiting.
Highly efficient Eu 2+ -activated phosphors are indispensable for solid-state lighting, yet the parasitic Eu 3+ emission remains a significant efficiency killer. Herein, we report a robust strategy to suppress Eu 3+ formation in Li 2 CaSiO 4 :Eu 2+ via a heterovalent substitution strategy by combining a two-step sintering process with charge compensation. We effectively promote the Eu 3+ →Eu 2+ reduction, boosting the external quantum efficiency (EQE) from 22% to 60%, and the deep defect levels induced by Si 4+ -P 5+ heterovalent substitution impart superior thermal stability to Li 2 CaSi 0.96 P 0.04 O 4 :Eu 2+ (94%@423 K), while retaining a remarkable 98% of its initial intensity after 30 days of water immersion. The as-fabricated phosphor-converted light-emitting diodes achieve a high color rendering index ( R a = 90.6) and a 50% reduction in blue-light hazard, demonstrating great potential for healthy illumination. Notably, this Eu 2+ stabilization strategy also effectively enhances the emission intensity of Li 2 CaGeO 4 :Eu 2+ and Li 2 MSiO 4 :Eu 2+ (M = Sr, Ba), thus establishing a general paradigm for the rational design of high-performance phosphors for next-generation light sources.
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