Insulating Boron Nitride Research Articles

A highly thermally conductive yet electrically insulating boron nitride nanosheets/polyetherimide composite with oriented structure

A highly thermally conductive yet electrically insulating boron nitride nanosheets/polyetherimide composite with oriented structure

Vertically aligned and conformal BN-coated carbon fiber to achieve enhanced thermal conductivity and electrical insulation of a thermal interface material

Due to excellent thermal conductivity, high aspect ratio, and low density, mesophase pitch-based carbon fibers (MPCFs) are highly desired in electronic packaging. However, their thermal conductivity is hard to present in the polymer matrix because of the disordered stacking and low filling. Moreover, few researches are focused on the enhancement of the electrical insulation performance for MPCFs. Herein, we report vertically aligned and insulating boron nitride (BN) coated carbon fiber (CF) powders as significant fillers for polymer composites, endowing markedly improved thermal conductivity and electrical insulation. The high-quality BN coating layer on the surface of the CF is produced by a cooling precipitation method and high-temperature treatment with ingenious use of solubility properties, exhibiting a conformal, dense, and highly crystalline structure. This preparation method overcomes the limitations of coating thickness and particle agglomeration, resulting in a 31-fold enhancement of the electrical resistivity of the CF powders. After orientation treatment in a silicone rubber matrix, such CF@BN-filled pads exhibit good thermal conductivity, significantly improved insulation performance, and excellent mechanical properties. Among them, the optimized pad achieves a thermal conductivity of 12.06 W m−1 K−1, a volume resistivity of 50 × 108 Ω cm and a breakdown voltage of 3100 V mm−1, exceptional flexibility, and a favorable compression ratio (@45 psi) of 41.7 %. This work provides unique insights into constructing carbon fiber fillers as well as the preparation of high thermal conductivity composites, thereby expanding the application scenarios of carbon fiber powder in electronic packaging.

Boosting the charge transport and stability of metal halide perovskite with boron nitride nanosheets for X-ray detection and imaging

Metal halide perovskites have been widely used in optoelectronic applications due to their excellent optoelectronic properties. However, ensuring their stability during operation remains a significant challenge. In this study, we investigated the charge carrier dynamics of perovskite films and devices, comparing those with and without the insertion of boron nitride on the grain boundaries. It was revealed that the charge transport and stability could be significantly enhanced with the present of boron nitride nanosheets on the grain boundaries. The incorporation of boron nitride led to a substantial improvement in charge carrier mobility and lifetime, without any noticeable changes in phase segregation or photostability. Moreover, the perovskite detectors incorporating boron nitride exhibited suppressed ion migration and dark current, while demonstrating an enhanced photoresponse and radiation exposure capability. These findings indicate that the addition of insulating boron nitride nanosheets acts as a stabilizer, enhancing the stability of both the perovskite thin films and the devices. Additionally, the incorporation of boron nitride significantly improved the device performance benefiting from the enhanced charge transport, indicating that the boron nitride nanosheets enhanced perovskite photodiodes possess great potential for X-ray detection and imaging.

Solar Cell Application of 1D Heterostructure Based on Single-Walled CNT

The experimental synthesis of one-dimensional (1D) van der Waals heterostructures, first introduced in 2020 [1], has attracted much research attention. Discussions upon this coaxial stack of different atomic layers are not only limited to synthesis and characteristics, but also extended to applications. Many unique properties of the 1D van der Waals heterostructures, such as the adjustable band gap, strong quenching of photoluminescence of MoS2 by inner single-walled CNT, enable this structure to be a potential active layer material for solar cells [2].For the synthesis of 1D van der Waals heterostructures, we first use dispersed high-purity semiconducting single-walled carbon nanotubes (s-SWCNT) solution obtained from Kataura group [3] as inner tube material. With an anodic aluminum oxide (AAO) membrane filter and HCl, we managed to fabricate a free-standing s-SWCNT film [4]. Then following our established CVD process [5], we are wrapping this inner s-SWCNT tube with an insulating boron nitride layer, and a semiconducting MoS2 layer. After that, the as-prepared 1D van der Waals heterostructures film will be utilized for solar cell fabrication.The solar cell is adopting an n-i-p structure, in the order of glass-ITO-SnO2-Active layer-Spiro-Au. After spin-coating and annealing SnO2 (electron transporting layer) onto ITO-patterned glass, the 1D van der Waals heterostructure film is laminated on the SnO2 layer. Spiro (hole transporting layer) will be then spin-coated onto the film. Finally, gold is vapor-deposited onto the device in a vacuum chamber, as the top electrode [6].Through photocurrent measurement of 1D van der Waals structure film using Esko film, a mixture of metallic-SWCNT and s-SWCNT, we found it is photosensitive with exposure to light and laser. The 1D van der Waals structure film using high-purity s-SWCNT is then expected to generate higher photocurrent, the experimental result will be updated in the future. By the IV measurement of the solar cell, we observed the photovoltaic effect of the device. Moreover, this new conceptual solar cell is believed to possess many advantages at the same time, such as flexibility, durability, non-toxicity, and sustainability [2]. However, further research on the choices of materials and optimizations of device parameters is still required in order to reach sufficient power conversion efficiency as a photovoltaic device.[1] R. Xiang et al., Science 367, 537–542 (2020)[2] R. Xiang et al., Natl Sci Open 1, 3 (2022)[3] J. Cui et al., ACS Appl. Nano Mater 2, 1, 343–350 (2019)[4] C. Zhang et al., ACS Nano 16, 11, 18630–18636 (2022)[5] M. Liu et al., ACS Nano 15, 5, 8418–8426 (2021)[6] J.-M. Choi et al, Adv. Funct. Mater. 32, 2204594 (2022)

A bead–string Co/C@BNNT nanocomposite: preparation and tunable electromagnetic wave absorption performance

A bead–string Co/C@BNNT nanocomposite was fabricated by in situ synthesis combined with the carbonization method using the Co-MOF ZIF-67 as the precursor and rigid insulating boron nitride nanotubes (BNNTs) as the carrier.

Experimental and Simulation Studies of the Effects of Nanosecond Pulse Frequency on the Dielectric Motion of BNNSs

Application of nanosecond pulsed electric fields to insulating nanoparticles can be used to prepare oriented high-performance composites, but the mechanism and related laws are still unclear. Therefore, in this article, highly insulating boron nitride nanosheet (BNNS) nanoparticles are selected, their alignment motions under different nanosecond intraburst frequencies (100 Hz–1 MHz) are studied for the first time in both experiments and simulations, and the two sets of results are compared and analyzed. The results show that the simulation results based on COMSOL are in good agreement with the experimental results, the variations in the local orientation angle with time and the local orientation time with intraburst frequency can be expressed by an allometric function, and the variation in the center-to-center distance with time can be described by an exponential decay function. Further experiments show that with the continuous application of the pulsed electric field, short chains of BNNSs continue to move to form longer chains, and long chains of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$342~\mu \text{m}$ </tex-math></inline-formula> form under the external application of the pulsed electric field for 3 min. The good agreement between experiments and simulations verifies the strong reliability of the proposed theory and the established mathematical model for predicting the orientation alignment motion of BNNS particles. The theory and simulation method can be used as effective tools to predict the trajectories of nanoparticles under a nanosecond pulsed electric field and their final alignment into chains.

Design of nanoscale capacitors based on metallic borophene and insulating boron nitride layers

In alignment with the efforts on miniaturizing the components of electronic devices with enhanced performance, we investigate a dielectric nanocapacitor (DNC) based on metallic borophene electrodes separated with insulating hexagonal boron nitride (h-BN) monolayers ($n=1--5$). The capacitive performance of the proposed DNC as a function of applied electric field ($\stackrel{P\vec}{E}$) and thickness of the dielectric material is examined by using ab initio methods. The borophene plates and h-BN monolayers are commensurate and coupled only with van der Waals interaction, which constitutes an ideal configuration as a DNC. It is found that a single h-BN layer is not thick enough as a spacer to hinder quantum tunneling effects, and similar to the case with no insulating layer, borophene electrodes are shorted. Being effective from two h-BN layers, the charge separation on borophene plates is attained via $\stackrel{P\vec}{E}$ in the vertical direction. The capacitance of the DNC rapidly saturates at $\stackrel{P\vec}{E}\ensuremath{\ge}0.1\phantom{\rule{0.28em}{0ex}}\mathrm{V}/\AA{}$ and reaches its maximum value of $0.77\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{F}/{\mathrm{cm}}^{2}$ for $n=2$. The capacitance decreases with an increasing number of insulating layers as the distance between electrodes enlarges and shows a similar trend that is expected from the classical Helmholtz model. Our results suggest metallic and lightweight borophene and insulating h-BN monolayers as ideal constituents for the DNC design.

One-Dimensional van der Waals Heterojunction Diode.

The synthesis of one-dimensional van der Waals heterostructures was realized recently, which offers alternative possibilities for prospective applications in electronics and optoelectronics. The even reduced dimension will enable different properties and further miniaturization beyond the capabilities of their two-dimensional counterparts. The natural doping results in p-type electrical characteristics for semiconducting single-walled carbon nanotubes and n-type for molybdenum disulfide with conventional noble metal contacts. Therefore, we demonstrate here a one-dimensional heterostructure nanotube, 11 nm wide, with the coaxial assembly of a semiconducting single-walled carbon nanotube, insulating boron nitride nanotube, and semiconducting molybdenum disulfide nanotube, which induces a radial semiconductor-insulator-semiconductor heterojunction. When opposite potential polarity was applied on a semiconducting single-walled carbon nanotube and molybdenum disulfide nanotube, respectively, the rectifying effect was materialized.

Boron nitride and molybdenum disulfide as 2D composite element selectors with flexible threshold switching

Abstract 2D composite nanomaterials of insulating boron nitride (BN) and semiconductor molybdenum disulfide (MoS2)-based flexible threshold switching selectors (Ag/BN+MoS2/Ag based on BM1 and BM2) are fabricated. Both selectors shown excellent bidirectional threshold switching characteristics. The assembled 1S1R unit comprising Ag/BN+MoS2/Ag based on BM1 selector and bipolar rewritable Ag/ZnO/Ag resistive switching memory shows the effectiveness of cross crosstalk suppression. The thermal conductivity of the functional layer based on BM2 decreasing to some extent with the content of BN decreasing, resulting in an increasing trend of Vhold compared with selector based on BM1. And the selectors of Ag/BN+MoS2/Ag based on BM2 were assembled with a unidirectional open WORM Ag/polyvinyl carbazole/Ag memory, it also shows a good effect in restraining the crosstalk. It has large developmental potentiality in flexible 2D composite nanomaterials threshold switching selector to restrain the crosstalk issue for a large RRAM array.

Realizing Rationally-Balanced Dielectric Properties in Fluoropolymer/Cr2AlC MAX Composites Modified by 2D-BN

Polymer/conductor composite dielectric materials have a high dielectric constant. In recent years, composite dielectrics have become a study hotspot in high-density energy storage capacitors. However, high dielectric loss and high electrical conductivity make the application of the composite materials very limited. In order to obtain composite materials with high dielectric constant, low dielectric loss and low conductivity, we added the insulating boron nitride (BN) filler into polymer/Cr2AlC composites. As a conductive filler, Cr2AlC ternary-layered-compound (MAX) ceramic has an interface polarization with the polymer matrix, thereby increasing the dielectric constant of the composites. The insulating BN has a very low electrical conductivity, which can effectively reduce the electrical conductivity and dielectric loss of the composites. Compared with the binary polymer/Cr AlC composite materials, the ternary polymer/Cr AlC/BN composite materials can achieve the low dielectric loss and low conductivity as well as properly-lowered dielectric constant. The ternary composite material filled with 10 wt% Cr2AlC and 2 wt% BN has a dielectric constant of about 30, a dielectric loss of about 0.7 and a conductivity of about 4.6×10− 7 S m−1 at 100 Hz. In this work, high-performance composite dielectrics were prepared through good cooperation between conductive and insulating ceramic fillers, which might provide an idea for design of promising energy storage capacitors.

Visualization of moiré superlattices.

Moiré superlattices in van der Waals heterostructures have given rise to a number of emergent electronic phenomena due to the interplay between atomic structure and electron correlations. Indeed, electrons in these structures have been recently found to exhibit a number of emergent properties that the individual layers themselves do not exhibit. This includes superconductivity1,2, magnetism3, topological edge states4,5, exciton trapping6 and correlated insulator phases7. However, the lack of a straightforward technique to characterize the local structure of moiré superlattices has thus far impeded progress in the field. In this work we describe a simple, room-temperature, ambient method to visualize real-space moiré superlattices with sub-5-nm spatial resolution in a variety of twisted van der Waals heterostructures including, but not limited to, conducting graphene, insulating boron nitride and semiconducting transition metal dichalcogenides. Our method uses piezoresponse force microscopy, an atomic force microscope modality that locally measures electromechanical surface deformation. We find that all moiré superlattices, regardless of whether the constituent layers have inversion symmetry, exhibit a mechanical response to out-of-plane electric fields. This response is closely tied to flexoelectricity wherein electric polarization and electromechanical response is induced through strain gradients present within moiré superlattices. Therefore, moiré superlattices of two-dimensional materials manifest themselves as an interlinked network of polarized domain walls in a non-polar background matrix.

Assessing corrosion resistance of two-dimensional nanomaterial-based coatings on stainless steel substrates.

Two-dimensional (2D) materials have elicited considerable interest in the past decade due to a diverse array of novel properties ranging from high surface to mass ratios, a wide range of band gaps (insulating boron nitride (BN) to semiconducting transition metal dichalcogenides), high mechanical strength and chemical stability. Given the superior chemo-thermo-mechanical properties, 2D materials may provide transformative solution to a familiar yet persistent problem of significant socio-economic burden: the corrosion of stainless steel (SS). With this broader perspective, we investigate corrosion resistance properties of SS-coated with 2D nanomaterials; molybdenum disulfide (MoS2), BN, bulk graphite in 3.5 wt% aqueous NaCl solution. The nanosheets were prepared by a novel liquid phase exfoliation technique and the coatings were made by a paint brush to achieve uniformity. Open circuit potential (OCP) and potentiodynamic plots indicate the best corrosion resistance is provided by the MoS2 coatings. Superior performance of the coating is attributed to low electronic conductivity, large flake size and uniform coverage of SS substrate, which probably impeded the corrosive ions from the solution from diffusing through the coating.

Controlling current flow in sintering: A facile method coupling flash with spark plasma sintering.

A facile method is described to couple flash sintering (FS) and spark plasma sintering (SPS). Flash spark plasma sintering (FSPS) combines advantages of both techniques: the use of pellet-shaped samples under mechanical load with the controlled passage of electric current through the sample. FSPS is realized by partially replacing graphite pressing tools (two punches and one matrix) used in standard SPS. An insulating boron nitride matrix substitutes the conducting graphite matrix to force the electric current through the sample. Additionally, external heating of the boron nitride matrix is implemented. Microstructures of standard and flash-SPS are compared using aluminum doped zinc oxide as an example. Scanning electron microscopy reveals that different microstructures are generated for SPS and FSPS. The new setups provide novel processing routes for different current sintering methods of materials under mechanical load and assist in identifying the role of the electric current or field in the microstructure.

Reinforcement of Polymer-Based Nanocomposites by Thermally Conductive and Electrically Insulating Boron Nitride Nanotubes

A detailed study has been undertaken of the mechanisms of stress transfer in a nanocomposite consisting of hexagonal boron nitride (hBN) nanotubes (BNNTs) in a poly(vinyl alcohol) (PVA) matrix base...

Effective boron doping in three-dimensional nitrogen-containing carbon foam with mesoporous structure for enhanced all-solid-state supercapacitor performance

Herein, we prepare three-dimensional B-doped N-containing carbon foams with a mesoporous structure by annealing boric acid–impregnated commercial melamine foam and characterize the obtained samples by a range of instrumental techniques. The chemical composition, structure, and electrochemical performance of B-doped N-containing carbon foams are shown to be dependent on annealing temperature (500–900 °C), e.g., increasing the annealing temperature from 500 to 700 °C results in the formation of a mesoporous structure and promotes B doping, which increases the concentration of carriers, the rate of ion transport and electrical conductivity. However, a further increase of annealing temperature from 700 to 900 °C leads to the collapse of pore structure and the formation of insulating boron nitride, causing electrochemical performance deterioration. As a result, optimal performance is observed for samples annealed at 700 °C (capacity = 462 mF cm−2 at a current density of 0.2 mA cm−2). More importantly, the supercapacitor has an obvious improvement in the rate capability. The successful fabrication of B-doped N-containing carbon foams and in-depth study of the electrochemical performance highlights the importance of tuning the concentration of doped heteroatoms, pore structure, and electrical conductivity for the design of carbon-based supercapacitors.

High-Performance WS2 Monolayer Light-Emitting Tunneling Devices Using 2D Materials Grown by Chemical Vapor Deposition.

The solid progress in the study of a single two-dimensional (2D) material underpins the development for creating 2D material assemblies with various electronic and optoelectronic properties. We introduce an asymmetric structure by stacking monolayer semiconducting tungsten disulfide, metallic graphene, and insulating boron nitride to fabricate numerous red channel light-emitting devices (LEDs). All the 2D crystals were grown by chemical vapor deposition (CVD), which has great potential for future industrial scale-up. Our LEDs exhibit visibly observable electroluminescence (EL) at both 5.5 V forward and 7.0 V backward biasing, which correlates well with our asymmetric design. The red emission can last for at least several minutes, and the success rate of the working device that can emit detectable EL is up to 80%. In addition, we show that sample degradation is prone to happen when a continuing bias, much higher than the threshold voltage, is applied. Our success of using high-quality CVD-grown 2D materials for red light emitters is expected to provide the basis for flexible and transparent displays.

Processable Thermally Conductive Polyurethane Composite Fibers

AbstractThe demand for wearable electronics has resulted in an increasing interest in the development of functional fibers, with a specific focus upon the development of electrically conductive fibers incorporable into garments. However, the production of thermally conductive fibers for heat dissipation has been largely neglected. Owing to the very rapid development of miniaturized wearable electronics, there is an increasing need for the development of thermally conductive fibers as heat sinks and thermal management processes. In this study, thermally conductive but electrically insulating boron nitride nanopowder (BNNP) fillers are used to effectively enhance the thermal conductivity and mechanical properties of elastomeric polyurethane fibers. Thermal conductivity enhancement of more than 160% is achieved at very low loadings of BNNP (less than 5 wt%) with an improvement in the mechanical properties of the unmodified fiber. These thermally conductive fibers are also incorporated into 3D textile structures as a proof of processability.

Thermal Percolation Threshold and Thermal Properties of Composites with High Loading of Graphene and Boron Nitride Fillers.

We investigated thermal properties of the epoxy-based composites with the high loading fraction-up to f ≈ 45 vol %-of the randomly oriented electrically conductive graphene fillers and electrically insulating boron nitride fillers. It was found that both types of the composites revealed a distinctive thermal percolation threshold at the loading fraction fT > 20 vol %. The graphene loading required for achieving thermal percolation, fT, was substantially higher than the loading, fE, for electrical percolation. Graphene fillers outperformed boron nitride fillers in the thermal conductivity enhancement. It was established that thermal transport in composites with high filler loadings, f ≥ fT, is dominated by heat conduction via the network of percolating fillers. Unexpectedly, we determined that the thermal transport properties of the high loading composites were influenced strongly by the cross-plane thermal conductivity of the quasi-two-dimensional fillers. The obtained results shed light on the debated mechanism of the thermal percolation, and facilitate the development of the next generation of the efficient thermal interface materials for electronic applications.

(Invited) Combination of Insulating Boron Nitride and Inert Gold Substrate As an Efficient Electrocatalysts for Oxygen Reduction Reaction and Hydrogen Evolution Reaction - Theoretical and Experimental Investigations

Large overpotential for oxygen reduction reaction (ORR) is one of the most serious problems in the development of fuel cells. Although Pt group metals are the most efficient electrocatalysts, world-wide efforts have been made to find alternative catalysts because of their high cost, less abundance, poor stability, and still sluggish kinetics. Recently we proposed theoretically that hexagonal boron nitride (h-BN) monolayer, which has similar geometric structure to the graphene but is an insulator with a wide band gap (5.8eV), can be used as an ORR catalyst [1-3]. DFT calculations for BN/Au(111) predicted the possible ORR activity of BN/Au(111) [3] and electrocatalytic activities of various types of BN were experimentally examined [3, 4]. The overpotential for ORR at Au electrode was reduced by ca. 100, ca. 270, and ca.150 mV by spin coating of the dispersion of BN nanotube (BNNT) and BN nanosheet (BNNS), and sputter deposition of BN, respectively, although oxygen is reduced to H2O2 by 2-electron reduction in all the cases, as theoretically predicted. The reason why the BNNS modification resulted in the highest activity is attributed to the presence of B-and/or N-edge structures based on theoretical investigation. While the BN modification was effective to improve ORR activity at Au electrode, it has no and negative effects at GC and Pt electrodes, respectively, suggesting the important role of BN-substrate interaction. One would expect higher ORR activity if we can increase the BN-Au interaction. The interaction was increased by depositing gold nanoclusters (Au-NCs) on BNNS, which was then placed on a Au electrode (Au-BNNS/Au). The decoration of BNNS with gold clusters lead to not only the reduction of overpotential for ORR further by ca. 50 mV, but also opening of a 4-electron reduction route to water, confirming the important role of Au-BN interaction for ORR [5,6]. The increase of the BN-Au interaction can be also achieved by using smaller sized BNNS. Indeed the smaller the BNNS size, the lower the ORR overpotential and the higher the fraction of 4-electron reduction [7]. The combination of BNNS-Au is proved to be a very active electrocatalyst for hydrogen evolution [8]. [1] A. Lyalin, K. Nakayama, K. Uosaki, and T. Taketsugu, J. Phys. Chem. C, 117 (2013) 21359. [2] A. Lyalin, A. Nakayama, K. Uosaki, and T. Taketsugu, Phys. Chem. Chem. Phys., 15 (2013) 2809. [3] K. Uosaki, G. Elumalai, H. Noguchi, T. Masuda, A. Lyalin, A. Nakayama, and T. Taketsugu, J. Am.Chem. Soc. 136 (2014) 6542. [4] G. Elumalai, H. Noguchi, and K. Uosaki, Phys. Chem. Chem. Phys., 16 (2014) 13755. [5] G. Elumalai, H. Noguchi, A. Lyalin, T. Taketsugu, and K. Uosaki, Electrochem. Commun. 66 (2016)53. [6] G. Elumalai, H. Noguchi, H. C. Dinh, and K. Uosaki, J. Electroanal. Chem., in press, DOI:10.1016/j.jelechem.2017.09.033 (2018). [7] H. C. Dinh, H. Noguchi, G. Elumalai, and K. Uosaki, unpublished results. [8] K. Uosaki, G. Elumalai, H. C. Dinh, A. Lyalin, T. Taketsugu, and H. Noguchi, Sci. Rep., 6 (2016)32217.

Insulating Boron Nitride Nanosheet on Inert Gold Substrate As a Highly Efficient Electrocatalyst for Hydrogen Evolution Reaction

Although hydrogen evolution reaction (HER) takes place readily at electrodes of Pt group metals and their alloys, for water electrolysis to become a practical hydrogen production process, cost reduction is essential and the use of expensive and less abundant Pt group metals must be avoided. Recently, inorganic catalysts such as nano-sized metal dichalcogenides such as MoS2 and WS2, which are semiconductors with layered structure, have been found to have high activity for HER and have drawn great attention due to their low cost and high chemical stability. Hexagonal boron nitride (h-BN) monolayer has similar geometric structure to that of graphene but it is an insulator with a wide band gap (˜5.8eV) and, therefore, is not considered as an electrocatalytic material. We, however, theoretically demonstrated that the band gap of h-BN monolayer is considerably reduced and h-BN becomes semiconducting if some defects are introduced and/or it is placed on metal substrates [1]. Theoretical investigation also suggested that h-BN would act as an effective electrocatalyst for oxygen reduction reaction (ORR) [2]. It was experimentally proved that Au electrodes modified with various types of h-BN indeed act as effective ORR electrocatalysts, although the overpotential for ORR is still high compared with Pt electrode and oxygen is mainly reduced to H2O2 via 2-electron process [2-4]. Considering the electrocatalytic activity of BN for ORR and relatively large hydrogen adsorption/storage ability of BN, electrocatalytic activity of BN nanosheet (BNNS) on Au electrode is examined [5]. Figure 1 shows linear sweep voltammograms (LSVs) of bare and BNNS modified Au, glassy carbon (GC), and Pt (v, vi) electrodes obtained in Ar saturated 0.5 M H2SO4 solution by scanning the potential negatively with 1 mV/s. Overpotential at Au electrode is reduced by ca. 250 mV by the BNNS modification, showing that BNNS indeed acts as an electrocatalyst for HER at Au electrode as does for ORR, although BNNS shows almost negative and no effect at Pt and GC electrodes, respectively, as observed for ORR.DFT calculations were performed to obtain free energy diagram for HER at various 2D BN nano-systems on Au(111) at equilibrium potential. Properties of the h-BN monolayer towards H adsorption are considerably modified by Au(111) substrate. Atoms at the edges of BNNS islands on Au(111) are found to provide energetically favored sites for adsorbed hydrogen, i.e., intermediate state, of HER and can act as good electrocatalytic sites for HER. Based on this theoretical consideration, further improvement of electrocatalytic activity for HER can be expected by increasing the fraction of atoms at the edges of BNNS on Au substrate. Fraction of edge atoms should be increased by decreasing the size of each BNNS at a given amount of BNNS on the surface. The overpotential decreased by decreasing the size of the BNNS as expected. The best result was obtained for the Au(111) electrode modified with the smallest BNNS used in the present study (BNNS(0.1-0.22 µm)/Au). The overpotential at BNNS(0.1-0.22 µm)/Au electrode is only 30 and 40 mV larger than that at Pt electrode at 5 mAcm-2 and 15 mAcm-2.