In-situ integration of multiple materials with well-defined interfaces as heterostructures is of great interest due to their unique properties and potential for new device functionality. Because of its polymorphism and diverse bonding geometries, borophene is a promising candidate for two-dimensional heterostructures, but suitable synthesis conditions have limited its potential applications. Toward this end, we demonstrate the vertical borophene and graphene heterostructures which form by epitaxial growth of borophene onto multilayer graphene on Cu substrates via chemical vapor deposition, where hydrogen and NaBH₄ are respectively used as the carrier gas and the boron source. The lattice structure of the as-synthesized borophene well coincides with the predicted α′-boron sheet. The borophene-based photodetector shows an excellent broadband photoresponse from the ultraviolet (255 nm) to the infrared (940 nm) wavelengths, with enhanced responsivity compared to pristine borophene or graphene photodetectors. This work informs emerging efforts to integrate borophene into nanoelectronic applications for both fundamental investigations and technological applications.

Borophene, as a rising-star monoelemental two-dimensional (2D) material, has motivated great interest because of its novel properties, such as anisotropic plasmonics, high carrier mobility, mechanical compliance, optical transparency, ultrahigh thermal conductance, and superconductivity. These properties make it an ideal candidate for use in the field of energy, sensors, and information storage. Stimulated by the realization of pioneering experimental works in 2015 and the follow-up synthesis experiments, a series of high-performance borophene-based devices in the fields, including supercapacitors, batteries, hydroelectric generators, humidity sensors, gas sensors, pressure sensors, and memories, have been experimentally reported in recent years, which are beneficial to the transition of borophene-based materials from experimental synthesis to practical application. Therefore, in addition to paying attention to the experimental preparation of borophene, significant efforts are needed to promote the advancement of related applications of borophene. In this review, after providing a brief overview of borophene evolution and synthesis, we mainly summarize the applications of borophene-based materials in energy storage, energy conversion, energy harvesting, sensors, and information storage. Finally, based on the current research status, some rational suggestions and discussions on the issues and challenges in the future research direction are proposed.

High-performance photonic nonvolatile memory which combines data storage and photosensing can achieve low power consumption and ensure computational energy efficiency. Heterostructure has been theoretically and experimentally proved to have synergistic effects between two materials, which can lead to promising electronic and optical properties for advanced optoelectronic devices. Herein, we report the preparation of borophene-ZnO heterostructures and their applications of broadband photonic nonvolatile memory. The memory shows a good switching ratio (5 × 10³) and long-term stability (3,600 s), which are superior to those of the pristine borophene or ZnO quantum dots (QDs). It is found that the memory shows a broad light response from ultraviolet (365 nm) to near infrared (850 nm). Besides, the SET voltage will decrease when the device is exposed to light, which can be attributed to the separation of holes and electrons in accelerating the formation of vacancy conductive filament. This work not only provides a promising material for next-generation photoelectric information, but also paves the way for borophene-based memory towards data storage devices.

Ternary materials composed of boron, carbon, and nitrogen have drawn tremendous attention because of their suitable band gap, high carrier mobility, and high thermal conductivity. The properties can effectively compensate for the deficiencies of other typical carbon-based and boron-based materials, such as graphene, borophene, and hexagonal boron nitride. Although the theoretical progress has advanced the development of ternary materials, it is still a great challenge to synthesize the new nanostructures with good crystallinity and high yield at low dimensional scales. Herein, we report that BC₂N quantum dots (QDs) can be successfully prepared by in-situ two-step thermal decomposition of sodium cyanoborohydride in a hydrogen-rich environment. The results show that the as-prepared BC₂N QDs have good crystallinity and high yield. The BC₂N QDs have an average lateral size of 3.7 nm and an average thickness of 2.83 nm. The experimental results show that the QDs are semiconducting with an optical band gap of 2.15 eV. Furthermore, a fabricated BC₂N QDs-based nonvolatile memory shows a low SET operating voltage (0.74 V) and a high ON/OFF ratio (more than 1.74 × 10³) as well as good stability.

High-performance gas sensing devices have been extensively studied in industrial production, clinical medicine and environmental monitoring. Among the materials used to fabricate gas sensors, two-dimensional (2D) materials are viewed as favorable candidate sensing materials because of their high surface-to-volume ratios, abundant surface activity, defect sites. However, gas sensors based on the previously reported 2D materials have some disadvantages such as poor air-stability and slow dynamic response. Recently, borophene, as a unique 2D material, has been theoretically predicted to have excellent gas sensing characteristic, especially for nitrogen dioxide (NO₂). However, the gas sensing property of borophene has not been still reported experimentally. Here, we report that a chemiresistive sensor device based on borophene shows high sensitivity, fast response, high selectivity, good flexibility and long-time stability. It is found that the sensor has a low experimental detection limit of around 200 ppb, a large detection range from 200 ppb to 100 ppm, and fast response time of 30 s and recovery time of 200 s at room temperature, which are remarkably superior to those of reported 2D materials. The underlying NO₂ sensing mechanism of borophene is revealed by first-principles calculations. In line with theoretical predication, it has also been confirmed experimentally that the borophene-based sensor has a unique selectivity to NO₂ compared with other common gases. Furthermore, the sensor also displays superior flexibility and stability under different bending angles. This study shows excellent electronic and sensing characteristic of borophene, which indicates that it has great potential application value in high-performance sensing and detection in the future.

Heterostructure has triggered a surge of interest due to its synergistic effects between two different layers, which contributes to desirable physical properties for extensive potential applications. Structurally stable borophene is becoming a promising candidate for constructing two-dimensional (2D) heterostructures, but it is rarely prepared by suitable synthesis conditions experimentally. Here, we demonstrate that a novel heterostructure composed of hydrogenated borophene and graphene can be prepared by heating the mixture of sodium borohydride and few-layered graphene followed by stepwise and in situ thermal decomposition of sodium borohydride under high-purity hydrogen as the carrier gas. The fabricated borophene-graphene heterostructure humidity sensor shows ultrahigh sensitivity, fast response, and long-time stability. The sensitivity of the fabricated borophene-based sensor is near 700 times higher than that of pristine graphene one at the relative humidity of 85% RH. The sensitivity of the sensor is highest among all the reported chemiresistive sensors based on 2D materials. Besides, the performance of the borophene-graphene flexible sensor maintains good stability after bending, which shows that the borophene-based heterostructures can be applied in wearable electronics. The observed high performance can be ascribed to the well-established charge transfer mechanism upon H₂O molecule adsorption. This study further promotes the fundamental studies of interfacial effects and interactions between boron-based 2D heterostructures and chemical species.