Nannan Han

The discovery of cathode materials that simultaneously exhibit high oxygen-reduction activity, robust stability, and low cost is pivotal to moving solid oxide fuel cells (SOFCs) from the laboratory into commercial deployment. To address this challenge, we compile the largest perovskite dataset to date parameterized by the oxygen tracer surface exchange coefficient (k^*). Using only readily obtainable elemental and structural descriptors, we develop machine-learning models that surpass existing approaches in both accuracy and computational efficiency. Specifically, by integrating Mahalanobis-distance-based applicability-domain analysis with random forest-enhanced property descriptors and support vector regression, we high-throughput-screen 1.3 million ABO3 compositions and curate a candidate list that balances thermodynamic stability, cost, and oxygen-reduction activity. Beyond prediction accuracy, SHAP interpretation reveals strong physical correlations between the enhanced descriptors and k^*, highlighting the coefficient of thermal expansion, O p-band center, and A-site ionic radius as the dominant factors governing oxygen exchange kinetics. Finally, we identify 209 promising perovskite cathodes predicted to outperform LSC in the low-temperature regime, offering promising directions for experimental realization of practical low-temperature SOFCs.

Dual modulation strategy of coordination asymmetry and curvature optimizes the atomic Fe sites, unlocking record-level quasi-solid-state Zn–air battery performance with a capacity of 1.56 Ah and cycling over 2000 h at −40 °C.

Two-dimensional topological insulators (TIs) show great potential applications in low-power quantum computing and spintronics due to the spin-polarized gapless edge states. However, the small bandgap limits their room-temperature applications. Based on first-principles calculations, a series of C₂X (X = H, F, Cl, Br and I) functionalized III–V monolayers are investigated. The nontrivial bandgaps of GaBi-(C₂X)₂, InBi-(C₂X)₂, TlBi-(C₂X)₂ and TlSb-(C₂X)₂ are found to between 0.223 and 0.807 eV. For GaBi-(C₂X)₂ and InBi-(C₂X)₂, the topological insulating properties originate from the s-px,y band inversion induced by the spin-orbital coupling (SOC) effect. While for TlBi-(C₂X)₂ and TlSb-(C₂X)₂, the topological insulating properties are attributed to the SOC effect-induced band splitting. The robust topological characteristics are further confirmed by topological invariants Z ₂ and the test under biaxial strain. Finally, two ideal substrates are predicted to promote the applications of these TIs. These findings indicate that GaBi-(C₂X)₂, InBi-(C₂X)₂, TlBi-(C₂X)₂ and TlSb-(C₂X)₂ monolayers are good candidates for the fabrication of spintronic devices.

This paper investigates the distributed formation control of a group of leader-following spacecraft with bounded actuation and limited communication ranges. In particular, connectivity-preserving and collision-avoidance controllers are proposed for the leader with constant or time-varying velocity, respectively. The communication graph between the spacecraft is modeled via a distance-induced proximity graph. By designing a virtual proxy for each spacecraft, the spacecraft–proxy couplings address the actuator saturation constraints. The inter-proxy dynamics incorporated with a bounded artificial potential function fulfill the coordination of all proxies. In addition, the bounded potential function can simultaneously tackle connectivity preservation and collision avoidance problems. The distributed formation controllers are proposed for multiple spacecraft with constant or time-varying velocities relative to the leader. A sliding mode control approach and the proxies’ dynamics are used in the design of a distributed cooperative controller for spacecraft to address the cooperative problem between the followers and the leader. Numerical simulations confirm the effectiveness of the anti-saturation distributed connectivity preservation controller.

The photoluminescence of 10% Ag-doped CsCu ₂ I ₃ can be enhanced by hydrostatic pressure. The photoluminescence mechanism is defect states emission.

Van der Waals (vdW) stacking of two-dimensional (2D) materials to create artificial structures has enabled remarkable discoveries and novel properties in fundamental physics. Here, we report that vdW stacking of centrosymmetric 2D materials, e.g., bilayer MoS ₂ (2LM) and monolayer graphene (1LG), could support remarkable second-harmonic generation (SHG). The required centrosymmetry breaking for second-order hyperpolarizability arises from the interlayer charge transfer between 2LM and 1LG and the imbalanced charge distribution in 2LM, which are verified by first-principles calculations, Raman spectroscopy, and polarization-resolved SHG. The strength of SHG from 2LM/1LG is of the same order of magnitude as that from the monolayer MoS ₂ , which is well recognized with strong second-order nonlinearity. The emergent SHG reveals that the interlayer charge transfer can effectively modify the symmetry and nonlinear optical properties of 2D heterostructures. It also indicates the great opportunity of SHG spectroscopy for characterizing interlayer coupling in vdW heterostructures.

Site-selective growth methods enable direct integration of two-dimensional materials into functional devices. This review focuses on different strategies for fabricating materials into defined locations.

Two-dimensional (2D) monolayer–bilayer (ML-BL) lateral junctions (LJs) have recently attracted attention due to their straightforward synthesis and resulting clean interface. Such systems consist of an extended ML with a secondary layer present only over half of the system, leading to an interface that is associated with the terminating edge of the secondary half layer. Our first-principles calculations reveal that the edges of the half layer completely lack reconstruction in the presence of unintentional dopants, in this case, Re. This observation is in startling contrast to the known physics of three-dimensional (3D) semiconductor surfaces where reconstruction has been widely observed. Herein, the electrostatics of the reduced dimensionality allows for greater separation between compensating defects, enabling dopants to remotely passivate edge states without needing to directly participate in the chemistry.