Stacking Fault Enriching the Electronic and Transport Properties of Few-Layer Phosphorenes and Black Phosphorus

Interface engineering is critical for enriching the electronic and transport properties of two-dimensional materials. Here, we identify a new stacking, named Aδ, in few-layer phosphorenes (FLPs) and black phosphorus (BP) based on first-principles calculation. With its low formation energy, the Aδ stacking could exist in FLPs and BP as a stacking fault. The presence of the Aδ stacking fault induces a direct to indirect transition of the band gap in FLPs. It also affects the carrier mobilities by significantly increasing the carrier effective masses. More importantly, the Aδ stacking enables the fabrication of a whole spectrum of lateral junctions with all the type-I, II, and III alignments simply through the manipulation of the van der Waals stacking without resorting to any chemical modification. This is achieved by the widely tunable electron affinity and ionization potential of FLPs and BP with the Aδ stacking

Large Gap Two-Dimensional Topological Insulators with the Significant Rashba Effect in Ethynyl and Methyl Functionalized PbSn Monolayers

Two-dimensional (2D) topological insulators (TIs) have recently attracted a great deal of attention due to their nondissipation electron transmission, stable performance, and easy device integration. However, a primary obstacle to influencing 2D TIs is the small bandgap, which limits their room-temperature applications. Here, we adopted first-principles to predict inversion-asymmetric group IV monolayers, PbSn­(C2H)2 and PbSn­(CH3)2, to be quantum spin Hall (QSH) insulators with large topological gaps of 0.586 and 0.481 eV, respectively. The nontrivial band topologies, which can survive in a wide range of strain, are characterized by topological invariants Z2, gapless edge states, and the Berry curvature. Another intriguing characteristic is the significant Rashba SOC effect which can also be tuned by feasible compressive and tensile strains. Meanwhile, the hexagonal boron nitride (h-BN) provides a suitable substrate for growth of these films without influencing their topological phases. These novel materials are expected to accelerate the development of advanced quantum devices

Coexistence of the Piezoelectricity and Intrinsic Quantum-Spin Hall Effect in GaTeS and InTeS Monolayers: Implications for Spintronic Devices

Multifunctional two-dimensional (2D) nanomaterials play an increasingly dominant role in academic researches and practical applications. In this work, the coexistence of the piezoelectricity and intrinsic quantum-spin Hall (QSH) effect is predicted in MTeS (M = Ga and In) monolayers (d11 = 3.988 pm V–1 for GaTeS and 8.687 pm V–1 for InTeS). When the Janus structure InGaTe2S2 is designed, the in-plane piezoelectric coefficient d11 is enhanced to 10.512 pm V–1, with QSH state remaining. Meanwhile, an intriguing vertical piezoelectric polarization appears, which is attributed to breaking of the reflection symmetry. Moreover, their topological phases are robust and can exist in a wide range of uniaxial strains. In brief, coupling of the topology and piezoelectricity in MTeS (M = Ga and In) monolayers is promising to produce potential applications in piezoelectric quantum and nano spintronic devices

Single Nickel Atom-Modified Phosphorene Nanosheets for Electrocatalytic CO₂ Reduction

Nowadays, carbon dioxide (CO2) produced by global energy consumption far exceeds what the environment can absorb. So, the world is seeking a way to control and reduce CO2 emissions. The electrocatalytic CO2 reduction reaction (CRR) can effectively convert this greenhouse gas into energy sources, thus providing a method to solve CO2 emission and energy crisis issues. However, only quite limited catalysts are capable of converting CO2 into high-value C1 products. Herein, four structures of single Ni atom-modified phosphorene, as an electrocatalyst for the CRR, have been studied by first-principles calculations based on density functional theory (DFT). The results show that a single Ni atom adsorbed on monoatomic defective phosphorene (Ni-D-BP) has higher long-term activity and stability, and better CRR selectivity against the hydrogen evolution reaction (HER). In particular, Ni-D-BP shows good selectivity for HCOOH with a limiting potential of −0.31 V. The production of CH3OH and CH4 has the same limiting potential of −0.98 V, indicating that Ni-D-BP also has good catalytic properties for CH3OH or CH4 production. This study can reveal the mechanism of the CRR for single Ni atom-modified phosphorene-based catalysts and provide a way to design electrocatalysts for the CRR on the atomic scale

In Situ Visualization of Structural Evolution and Fissure Breathing in (De)lithiated H₂V₃O₈ Nanorods

Layered H2V3O8 material consisting of V3O8 layers features the elastic space for buffering volume change upon repeated ion (de)­intercalations. However, its ion transport and phase transformations still remain largely unknown due to lack of direct evidence. Here we employ in situ transmission electron microscopy to revisit this material carefully. Upon lithiation, the localized phase transformation from H2V3O8 to V2O3 via an intermediate VO2 phase was observed, and large structural fissures gradually formed. Unexpectedly, the large fissures were able to self-heal during delithiation with the VO2 phase as the delithiated product. The fissures could appear and disappear alternately upon subsequent (de)­lithiation, in which a stable and reversible phase transformation between V2O3 and VO2 phases was established. These unreported findings are expected to call for renewed attention to this electrode material for a more comprehensive understanding in rechargeable metal-ion batteries

In Situ Visualization of Structural Evolution and Fissure Breathing in (De)lithiated H₂V₃O₈ Nanorods

Layered H2V3O8 material consisting of V3O8 layers features the elastic space for buffering volume change upon repeated ion (de)­intercalations. However, its ion transport and phase transformations still remain largely unknown due to lack of direct evidence. Here we employ in situ transmission electron microscopy to revisit this material carefully. Upon lithiation, the localized phase transformation from H2V3O8 to V2O3 via an intermediate VO2 phase was observed, and large structural fissures gradually formed. Unexpectedly, the large fissures were able to self-heal during delithiation with the VO2 phase as the delithiated product. The fissures could appear and disappear alternately upon subsequent (de)­lithiation, in which a stable and reversible phase transformation between V2O3 and VO2 phases was established. These unreported findings are expected to call for renewed attention to this electrode material for a more comprehensive understanding in rechargeable metal-ion batteries

In Situ Visualization of Structural Evolution and Fissure Breathing in (De)lithiated H₂V₃O₈ Nanorods

Layered H2V3O8 material consisting of V3O8 layers features the elastic space for buffering volume change upon repeated ion (de)­intercalations. However, its ion transport and phase transformations still remain largely unknown due to lack of direct evidence. Here we employ in situ transmission electron microscopy to revisit this material carefully. Upon lithiation, the localized phase transformation from H2V3O8 to V2O3 via an intermediate VO2 phase was observed, and large structural fissures gradually formed. Unexpectedly, the large fissures were able to self-heal during delithiation with the VO2 phase as the delithiated product. The fissures could appear and disappear alternately upon subsequent (de)­lithiation, in which a stable and reversible phase transformation between V2O3 and VO2 phases was established. These unreported findings are expected to call for renewed attention to this electrode material for a more comprehensive understanding in rechargeable metal-ion batteries

In Situ Visualization of Structural Evolution and Fissure Breathing in (De)lithiated H₂V₃O₈ Nanorods

Layered H2V3O8 material consisting of V3O8 layers features the elastic space for buffering volume change upon repeated ion (de)­intercalations. However, its ion transport and phase transformations still remain largely unknown due to lack of direct evidence. Here we employ in situ transmission electron microscopy to revisit this material carefully. Upon lithiation, the localized phase transformation from H2V3O8 to V2O3 via an intermediate VO2 phase was observed, and large structural fissures gradually formed. Unexpectedly, the large fissures were able to self-heal during delithiation with the VO2 phase as the delithiated product. The fissures could appear and disappear alternately upon subsequent (de)­lithiation, in which a stable and reversible phase transformation between V2O3 and VO2 phases was established. These unreported findings are expected to call for renewed attention to this electrode material for a more comprehensive understanding in rechargeable metal-ion batteries

In Situ Visualization of Structural Evolution and Fissure Breathing in (De)lithiated H₂V₃O₈ Nanorods

Layered H2V3O8 material consisting of V3O8 layers features the elastic space for buffering volume change upon repeated ion (de)­intercalations. However, its ion transport and phase transformations still remain largely unknown due to lack of direct evidence. Here we employ in situ transmission electron microscopy to revisit this material carefully. Upon lithiation, the localized phase transformation from H2V3O8 to V2O3 via an intermediate VO2 phase was observed, and large structural fissures gradually formed. Unexpectedly, the large fissures were able to self-heal during delithiation with the VO2 phase as the delithiated product. The fissures could appear and disappear alternately upon subsequent (de)­lithiation, in which a stable and reversible phase transformation between V2O3 and VO2 phases was established. These unreported findings are expected to call for renewed attention to this electrode material for a more comprehensive understanding in rechargeable metal-ion batteries

In Situ Visualization of Structural Evolution and Fissure Breathing in (De)lithiated H₂V₃O₈ Nanorods

Layered H2V3O8 material consisting of V3O8 layers features the elastic space for buffering volume change upon repeated ion (de)­intercalations. However, its ion transport and phase transformations still remain largely unknown due to lack of direct evidence. Here we employ in situ transmission electron microscopy to revisit this material carefully. Upon lithiation, the localized phase transformation from H2V3O8 to V2O3 via an intermediate VO2 phase was observed, and large structural fissures gradually formed. Unexpectedly, the large fissures were able to self-heal during delithiation with the VO2 phase as the delithiated product. The fissures could appear and disappear alternately upon subsequent (de)­lithiation, in which a stable and reversible phase transformation between V2O3 and VO2 phases was established. These unreported findings are expected to call for renewed attention to this electrode material for a more comprehensive understanding in rechargeable metal-ion batteries