Leilei Yin,Shuai Zhang,Mingzi Sun,Siyuan Wang,Bolong Huang,Yaping Du
For current single-atom catalysts (SACs), modulating the coordination environments of rare-earth (RE) single atoms with complex electronic orbital and flexible chemical states is still limited. Herein, cerium (Ce) SAs supported on a P, S, and N co-doped hollow carbon substrate (Ce SAs/PSNC) for the oxygen reduction reaction (ORR) are reported. The as-prepared Ce SAs/PSNC possesses a half-wave potential of 0.90 V, a turnover frequency value of 52.2 s −1 at 0.85 V, and excellent stability for the ORR, which exceeds the commercial Pt/C and most recent SACs. Ce SAs/PSNC-based liquid zinc–air batteries (ZABs) exhibit a high and stable open-circuit voltage of 1.49 V and a maximum power density of 212 mW cm −2 . As the catalyst of the air cathode, it also displays remarkable performance in flexible electronic devices. Theoretical calculations reveal that the introduction of S and P sites induces significant electronic modulations to the Ce SA active sites. The P and S dopings promote the electroactivity of Ce SAs and improve the overall site-to-site electron transfer within the Ce SAs/PSNC. This work offers a unique perspective for modulating RE-based SACs in a complex coordination environment toward superior electrocatalysis and broad applications in energy conversion and storage devices.
The development of oxygen reduction reaction (ORR) catalysts with high activity, stability, and economic applicability plays a decisive role in reducing expenses and enhancing the discharge performance of seawater-based zinc-air batteries (SWZABs). Co- and Fe-based single-atom catalysts (M-N4-C) with metal-N4 structure offer advantages of well-defined active structure and high active site utilizations. However, the oxygen electrocatalytic performance of M-N4-C remains a formidable challenge due to the highly stable centrosymmetric electronic structure. To overcome the dilemma, we develop a Co-N4Cl-C with axial coordination of Cl atoms. The axial coordination drags the Co atoms out of the Co-N4 centrosymmetric configuration. This alters the electronic configuration of Co single-atom sites, resulting in a valence state change from +1.83 to +0.67 and forming a localized negative charge environment. These alternations enhance the electronic orbital overlap between Co single-atom sites and oxygen species, promote the rapid evolution of *OOH intermediates, and inhibit the adsorption of toxic Cl- ions, ensuring the ORR kinetics and stability. Co-N4Cl-C exhibits a high oxygen reduction onset potential of 1.05 mV and a half-wave potential of 0.88 mV vs. the reversible hydrogen electrode. The SWZAB, featuring a Co-N4Cl-C catalyst cathode, Zn anode, and NaCl electrolyte supplemented with KOH, reaches a discharge voltage platform of 1.27 V and a peak power density of 179 mW·cm-2, even at a current density of 10 mA·cm-2. This study sheds important light on advancing single-atom catalysts with superior ORR performance and economic viability.
Compared with other fluorescent crystal phases, garnet has better structural stability in a glass matrix and renders precisely controllable emissions due to the abundant lattice control positions. In this work, we regulate the coordination field of Ce 3+ ion based on the co-substitution method and achieve the spectra regulation in the yellow–green range. We used Ba 2+ –Si 4+ cations to replace Y 3+ –Al 3+ cations in Y 3 Al 5 O 12 (YAG) matrix to obtain blue-shift of the emission peak from 552 to 539 nm. The centroid shift and crystal field splitting decrease with the decreasing covalency of the bond between the Ce 3+ ion and the surrounding anions owing to the higher electronegativity of Si 4+ ions than Al 3+ ions. The corresponding fluorescent films were prepared by a low-temperature co-sintering process based on the as-made Ba 2+ –Si 4+ co-substituted phosphor. X-ray powder diffractometer and scanning electron microscopy images showed that the fluorescence crystals were less eroded and evenly dispersed in the glass matrix. Spectral analysis showed that the garnet phase was protected by using lead-free borosilicate glass with a low melting point, and the quantum efficiency of phosphor-in-glass (PiG) retains 98% of the corresponding phosphor. By adjusting the ratio of garnet phosphor to commercial red nitride phosphors, a warm white fluorescence with a color rendering index of 80.3 and color temperature of 3899 K was obtained. The prepared warm white film has potential application value in the whole spectra field.
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