Physical Chemistry Chemical Physics最新文献

Two-dimensional multiferroic materials, which exhibit both ferroelectricity and ferromagnetism, have drawn significant interest due to their capability to control electronic and magnetic properties via polarization switching. In this work, we designed a multiferroic van der Waals heterostructure (vdWH) made of 2D ferromagnetic Cr₂Cl₃S₃ and ferroelectric Ga₂O₃, and examined its structural, electronic, and magnetic properties through first-principles calculations. The results demonstrate that by manipulating the polarization state of Ga₂O₃, the Cr₂Cl₃S₃(Cl)/Ga₂O₃ vdWH can reversibly switch between semiconductor and half-metal, whereas the Cr₂Cl₃S₃(S)/Ga₂O₃ vdWH can transition reversibly between semiconductor and metal. These reversible transitions are attributed to the shift in band alignment induced by interlayer charge transfer. Notably, as the spintronic properties of the Cr₂Cl₃S₃(S)/Ga₂O₃ vdWH change, its easy magnetization axis also switches from in-plane to out-of-plane. The switchable electrical control of heterostructures by ferroelectric Ga₂O₃ is nonvolatile. These findings are important for understanding ferroelectric control of spintronics and electromagnetic coupling and provide a potential route for developing multiferroic memory devices.

NaNiO₂ is a layered material composed of alternating NaO₆ and NiO₆ octahedra, which undergoes an insulator-metal transition (IMT) from a monoclinic insulating phase to a metallic phase at approximately 480 K. Although this phase transition has been experimentally observed, its microscopic mechanism remains unclear, particularly regarding the role of Jahn-Teller (JT) distortion and the nature of the structural dynamics during the transition. In this work, we carry out a comprehensive first-principles study to address these issues. Our results show that the IMT is primarily driven by the gradual disappearance of the JT distortion of Ni³⁺, which restores the e_g orbital degeneracy and enables electronic delocalization. Furthermore, potential energy surface analysis and phonon spectrum calculations reveal that this process follows a displacive phase transition pathway, consistent with experimental observations. These findings provide, for the first time, a theoretical explanation of the microscopic mechanism underlying the IMT in NaNiO₂, thereby clarifying its structural-electronic interplay and offering new insights into the phase transition behavior of transition-metal oxides for future material applications.

Supported gold catalysts are fundamentally and practically important for hydrogenation reactions due to their unique electronic properties and catalytic activity. In this work, Au nanoparticles were successfully deposited onto an In₂O₃ support via a deposition-precipitation method to form a Au/In₂O₃ catalyst, which was subsequently evaluated for CO₂ hydrogenation under atmospheric pressure. This catalyst exhibits outstanding low-temperature activity for the reverse water gas shift (RWGS) reaction, achieving a CO₂ conversion of 21.3%, a CO selectivity of 100%, and a CO formation rate of 0.30 mmol_CO g_cat^-1 min^-1 at 350 °C. Characterization results reveal that Au nanoparticles are uniformly dispersed on the In₂O₃ surface, accompanied by charge transfer from Au to the In₂O₃ support. This strong electronic metal-support interaction (EMSI) results in the formation of positively charged Au^δ+ species, which facilitates H₂ dissociation. Meanwhile, the generation of surface oxygen vacancies on In₂O₃ is promoted, enhancing CO₂ adsorption and activation. These synergistic effects between Au nanoparticles and In₂O₃ account for the superior RWGS activities of the Au/In₂O₃ catalyst.