High sulfur resistance and high stability of catalysts are crucial for the catalytic decomposition of sulfur-containing volatile organic compounds. In this work, compared to 5Ce-MCM-41, the 5Cr-MCM-41 catalyst exhibited ultra-stability (no activity loss at 600 h) and higher sulfur resistance. The physical structure and chemical characteristics of the catalysts were analyzed by XRD , H 2 -TPR, NH 3 -TPD, CO 2 -TPD, XPS , and TEM. Combining the characterization results, we found that the 5Cr-MCM-41 catalyst presented outstanding catalytic performance due to superior reducibility and appropriate acidity, which results in the conversion of most of the C and S elements in the CH 3 SH to the gas-phase coke- and sulfur-containing products rather than accumulating on the catalyst surface. Meanwhile, the catalytic performance, reaction path, and deactivation mechanism of rare earth metal (Ce) and transition metal (Cr) modified MCM-41 catalysts were systematically investigated by in situ DRIFTS and DFT calculations. Additionally, a new active phase (sulfide state Cr 2 S 3 ) was proposed and proved via accurately designed experiments, which plays a significant role in the collaborative removal of CH 3 SH with hexavalent chromium (Cr(VI)). These findings are beneficial for designing high sulfur resistance catalysts for the removal of CH 3 SH and other sulfur-containing products.
As for nonlayered 2D polymorphic materials, especially for Cr-based chalcogenides, large-area thin film growth with phase control is considered the most important synthesis challenge for magnetic, electronic, and optoelectronic devices. However, the synthesis methods of large continuous thin films for nonlayered 2D materials are still limited and rarely reported, also for the phase control growth, which is inhibited by isotropic 3D growth and similar Gibbs free energy for different phases. Herein, enhanced mass transport chemical vapor deposition is established to achieve the control synthesis of trigonal Cr 2 S 3 thin films, in which the stable boundary layer supplies the continuous reaction species and tunes the reaction kinetics. The trigonal phase formation is confirmed by atomic structure characterization, optical absorption and piezoelectric measurements, demonstrating unique physical properties different from rhombohedral phase. The trigonal Cr 2 S 3 thin films show obvious layer independent and dissimilar angle-resolved harmonic generation, indicating the surface broken symmetry that can be understood by the combination of negligible piezoelectric response for bulk. The work presents the large-area synthesized strategy by the modification of mass transport for nonlayered 2D materials with new phase formation and establishes the surface symmetry breaking dominated SHG mechanism for future nonlinear optical materials.
Exploration for the new members of air-stable 2D antiferromagnetic magnets to widen the magnetic families has drawn great attention due to its potential applications in spintronic devices. In addition to seeking the intrinsic antiferromagnets, externally introducing antiferromagnetic ordering in existing 2D materials, such as structural regulation and phase engineering, may be a promising way to modulate antiferromagnetism in the 2D limit. In this work, the in situ nitrogen doping growth of ultrathin 2D Cr2S3nanoflakes has been achieved. Antiferromagnetic ordering in 2D Cr2S3nanoflakes can be triggered by nitrogen doping induced new phase (space group P3¯1c). This work provides a new route to realize antiferromagnetism in atomically thin 2D magnets and greatly extend applications of 2D magnets in valleytronics and spintronics.Keywords:2D magnetic materials;in situ nitrogen doping;antiferromagnetism
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