Black phosphorene/SnSe van der Waals heterostructure as a promising anchoring anode material for metal-ion batteries

Black phosphorene (BP) is a glowing two-dimensional semiconducting layer material for cutting-edge microelectronics, with high carrier mobility and thickness-dependent band gap. Here, based on van der Waals (vdW)-corrected first-principles approaches, we investigated stacked BP/tin selenide (BP/SnSe) vdW heterostructure as an anode material for metal ion batteries, which exhibits a significant theoretical capacity, along with relatively durable binding strength compared to the constituent BP and SnSe monolayers. Our calculations demonstrated that the Li/Na adatom favors insertion into the interlayer region of BP/SnSe vdW heterostructure owing to synergistic interfacial effect, resulting in comparable diffusivity to the BP and SnSe monolayers. Subsequently, the theoretical specific capacities for Li/Na are found to be as high as 956.30 mAhg-1and 828.79 mAhg-1, respectively, which could be attributed to the much higher storage capacity of Li/Na adatoms in the BP/SnSe vdW heterostructure. Moreover, the electronic structure calculations reveal that a large amount of charge transfer assists in semiconductor-to-metallic transition upon lithiation/sodiation, ensuring good electrical conductivity. These simulations verify that the BP/SnSe vdW heterostructure has immense potential for application in the design of metal-ion battery technologies.

High thermoelectric performance of two-dimensional SiPGaS/As heterostructures

Thermoelectric technology holds great promise as a green and sustainable energy solution, generating electric power directly from waste heat. Herein, we investigate the thermoelectric properties of SiPGaS/As van der Waals heterostructures by using computations based on density functional theory and semiclassical Boltzmann transport theory. Our results show that both models of SiPGaS/As van der Waals heterostructures have low lattice thermal conductivity at room temperature (300 K). Applying 4% tensile strain to the models leads to a significant enhancement in the figure of merit (ZT), with model-I and model-II exhibiting ZT improvements of up to 24.5% and 14.8%, respectively. Notably, model-II outperforms all previously reported heterostructures in terms of ZT value. Additionally, we find that the maximum thermoelectric conversion efficiency (η) for model-II at 4% tensile strain reaches 23.98% at 700 K. Our predicted ZT_avg > 1 suggests that these materials have practical potential for thermoelectric applications over a wide temperature range. Overall, our findings offer valuable insights for designing better thermoelectric materials.

Recent progress of two-dimensional heterostructures for thermoelectric applications

The rapid development of synthesis and fabrication techniques has opened up a research upsurge in two-dimensional (2D) material heterostructures, which have received extensive attention due to their superior physical and chemical properties. Currently, thermoelectric energy conversion is an effective means to deal with the energy crisis and increasingly serious environmental pollution. Therefore, an in-depth understanding of thermoelectric transport properties in 2D heterostructures is crucial for the development of micro-nano energy devices. In this review, the recent progress of 2D heterostructures for thermoelectric applications is summarized in detail. Firstly, we systematically introduce diverse theoretical simulations and experimental measurements of the thermoelectric properties of 2D heterostructures. Then, the thermoelectric applications and performance regulation of several common 2D materials, as well as in-plane heterostructures and van der Waals heterostructures, are also discussed. Finally, the challenges of improving the thermoelectric performance of 2D heterostructures materials are summarized, and related prospects are described.

High-Throughput Prediction of the Band Gaps of van der Waals Heterostructures via Machine Learning

Van der Waals heterostructures offer an additional degree of freedom to tailor the electronic structure of two-dimensional materials, especially for the band-gap tuning that leads to various applications such as thermoelectric and optoelectronic conversions. In general, the electronic gap of a given system can be accurately predicted by using first-principles calculations, which is, however, restricted to a small unit cell. Here, we adopt a machine-learning algorithm to propose a physically intuitive descriptor by which the band gap of any heterostructures can be readily obtained, using group III, IV, and V elements as examples of the constituent atoms. The strong predictive power of our approach is demonstrated by high Pearson correlation coefficient for both the training (292 entries) and testing data (33 entries). By utilizing such a descriptor, which contains only four fundamental properties of the constituent atoms, we have rapidly predicted the gaps of 7140 possible heterostructures that agree well with first-principles results for randomly selected candidates.

Transient absorption measurements of interlayer charge transfer in a WS2/GeS van der Waals heterostructure

We introduce germanium sulfide (GeS) as a new layered material for the fabrication of two-dimensional van der Waals materials and heterostructures. Heterostructures of WS₂/GeS were fabricated using mechanical exfoliation and dry transfer techniques. Significant photoluminescence quenching of WS₂ in the heterostructures indicates efficient charge transfer. Transient absorption measurements were performed to study the dynamics of charge transfer. The results show that the heterostructure forms a type-II band alignment with the conduction band minimum and valence band maximum located in the WS₂ and GeS layers, respectively. The ultrafast hole transfer from WS₂ to GeS is confirmed by the faster decay of the lower peak value of the differential reflection signal in the heterostructure sample, in comparison to the WS₂ monolayer. These results introduce GeS as a promising semiconductor material for developing new novel heterostructures.

Black phosphorene/blue phosphorene van der Waals heterostructure: a potential anode material for lithium-ion batteries

Van der Waals (vdW) heterostructure-based electrodes have invoked tremendous research interest due to their intriguing properties and their capability to break the limitations of the restricted properties of single-material systems. Herein, based on first-principles approaches, we propose that the black phosphorene/blue phosphorene (BLK-P/BLE-P) vdW heterostructure can be a capable anode material for power-driving lithium-ion batteries (LIBs), as it exhibits a large theoretical capacity, together with a relatively strong binding strength compared with the individual BLK-P and BLE-P monolayers. Our calculation results show that the Li adatom prefers to intercalate into the interlayer of the BLK-P/BLE-P vdW heterostructure due to the synergistic interfacial effect, resulting in a high binding strength and a diffusivity comparable to the BLK-P and BLE-P monolayers. Subsequently, the theoretical specific capacity is found to be as high as 552.8 mA h g^-1, which can be attributed to the much higher storage capacity of Li adatoms in the BLK-P/BLE-P vdW heterostructure. Furthermore, electronic structure calculations reveal that a large amount of charge transfer assists in semiconductor to metallic transition upon lithiation, which would ensure good electrical conductivity. These simulations prove that the BLK-P/BLE-P heterostructure has great potential in LIBs and is essential for future battery design.

Strong interlayer coupling in two-dimensional PbSe with high thermoelectric performance

It was generally believed that weak van der Waals interactions exist between neighboring layers in the two-dimensional group-IV chalcogenides. Using PbSe as a prototypal example, we find additional strong coupling between the Pb-Pb layers, as evidenced by detailed analysis of the differential charge density plot. The coupling is covalent-like and can be fine-tuned to obviously reduce the phonon thermal conductivity but slightly change the electronic transport of PbSe layer. As a consequence, a maximumZTvalue of 2.5 can be realized at 900 K for thep-type system. Our work also offers an effective and feasible design strategy to enhance the thermoelectric performance of similar layered structures.