Stable boron nitride nanocomposites based membranes for high-efficiency proton conduction

The Application of 2D Graphitic Carbon Nitride (g-C3N4) and Hexagonal Boron Nitride (h-BN) in Low-Temperature Fuel Cells: Catalyst Supports, ORR Catalysts, and Membrane Fillers

In recent years, two-dimensional (2D) graphitic carbon nitride (g-C3N4) and hexagonal boron nitride (h-BN) have gained remarkable attention due to their resemblance to graphene. These materials have a wide range of applications in energy and other sustainable fields, including heterogeneous catalysis and photocatalysis. g-C3N4 and h-BN can play different roles in low-temperature fuel cells. They can be used as catalyst supports, catalysts for oxygen reduction, and membrane fillers. In this work, the application of pure and doped g-C3N4 and h-BN, alone or as composite materials, in low-temperature fuel cells is overviewed.

Graphene Coating of Nafion Membranes for Enhanced Fuel Cell Performance

Electrochemically exfoliated graphene (e-G) thin films on Nafion membranes exhibit a selective barrier effect against undesirable fuel crossover. This approach combines the high proton conductivity of state-of-the-art Nafion and the ability of e-G layers to effectively block the transport of methanol and hydrogen. Nafion membranes are coated with aqueous dispersions of e-G on the anode side, making use of a facile and scalable spray process. Scanning transmission electron microscopy and electron energy-loss spectroscopy confirm the formation of a dense percolated graphene flake network, which acts as a diffusion barrier. The maximum power density in direct methanol fuel cell (DMFC) operation with e-G-coated Nafion N115 is 3.9 times higher than that of the Nafion N115 reference (39 vs 10 mW cm^-2@0.3 V) at a 5M methanol feed concentration. This suggests the application of e-G-coated Nafion membranes for portable DMFCs, where the use of highly concentrated methanol is desirable.

Challenges and issues with the performance of boron nitride rooted membrane for gas separation

Various fillers such as zeolites, metal-organic framework, carbon, metal framework, graphene, and covalent organic framework have been incorporated into the polymers. However, these materials are facing issues such as incompatibility with the polymer matrix, which leads to the formation of non-selective voids and thus, reduces the gas separation properties. Recent studies show that hexagonal boron nitride (h-BN) possesses attractive characteristics such as high aspect ratio, good compatibility with polymer materials, enhanced gas barrier performance, and improved mechanical properties, which could make h-BN the potential candidate to replace conventional fillers. The synthesis of materials and membranes is the subject of this review, which focuses on recent developments and ongoing problems. Additionally, a summary of the mathematical models that were utilised to forecast how well polymer composites would perform in gas separation is provided. It was found in the previous studies that tortuosity is the governing factor for the determination of the effectiveness of a nanofiller as a gas barrier enhancer in polymer matrices. The shape of the nanofiller particles and sheets, disorientation and distribution of the nanofillers within the polymer matrix, state of aggregation and rate of reaggregation of the nanofiller particles, as well as the compatibility of the nanofiller with the polymer matrix all played a significant role in determining how well a particular nanofiller will perform in enhancing the gas barrier properties of the nanocomposites. For this purpose, this review has been focused not only on the experimentation work but also on the effect of tortuosity, exfoliation quality, compatibility, disorientation, and reaggregation of nanofillers.

Bidirectional Superionic Conduction in Surface-Engineered 2D Hexagonal Boron Nitrides

We designed functionalized hexagonal boron nitride (FhBN) nanoflakes with high proton conductivity in both in- and through-plane directions as next generation polymer electrolyte membranes (PEMs) for energy storage and conversion systems. The synthesis and functionalization of hBN nanoflakes with sulfonic acid (SA) groups are obtained by one-step and in situ liquid-phase exfoliation with excellent dispersibility and stability over a period of three months. The physico/chemical properties of FhBN nanoflakes were investigated by different spectroscopic and microscopic characterization, confirming chemical interactions between hBN lattice and SA groups. High concentrations (65 and 75 wt %) of FhBN nanoflakes composed with Nafion solution formed stable FhBN-Nafion nanocomposite PEMs, offering extra proton conduction sites, doubling ion-exchange capacity, and reducing the swelling ratio compared to those of Nafion. Our results demonstrate that both the in-plane and through-plane proton conductivities of FhBN-Nafion PEMs significantly improve under various conditions comparative to that of Nafion. The maximum values of both in- and through-plane conductivities for FhBN75%-Nafion PEM at 80% of humidity and 80 °C are 0.41 and 0.1 S·cm^-1, respectively, which are 7 and 14 times higher than those of Nafion. The bidirectional superionic transport in highly concentrated FhBN PEMs is responsible for outstanding properties, useful for electrochemical energy devices.

Performance enhancement of direct methanol fuel cells using a methanol barrier boron nitride–Nafion hybrid membrane

Sulfonated hexagonal boron nitride is explored as a potential filler to prepare Nafion hybrid membranes for direct methanol fuel cell (DMFC) applications.

Boron nitride: a promising material for proton exchange membranes for energy applications

Boron nitride (BN) is an exciting material and has drawn the attention of researchers for the last decade due to its surprising properties, including large surface area, thermomechanical stability, and high chemical resistance. Functionalization of BN is a new area of interest to build up novel properties and applications of BN. BN and functionalized BN are promising membrane materials and show enormous advantages ascribed to their simple synthesis, high surface area, mechanical and thermal stability, and distinctive mechanical properties. BN-based proton exchange membranes show improvement in their physicochemical, electrochemical, thermal, mechanical, and barrier properties. Only a few research studies have been carried out on BN-based highly stable proton exchange membranes (PEMs) for various electrochemical applications. In this review, we discuss the recent advances in the functionalization of BN by different methods. The synthesis of different proton exchange membranes has also been discussed in this article. In addition, the potential applications of hybrid proton exchange membranes have also been mentioned.