3D white graphene foam scavengers: vesicant-assisted foaming boosts the gram-level yield and forms hierarchical pores for superstrong pollutant removal applications

Abstract

Three-dimensional (3D) nanostructures assembled with one-or few-layered ultrathin two-dimensional (2D) crystals have triggered great interest in energy and environmental applications. Here, we introduce a gas-foaming process in an hexagonal boron nitride (h-BN) ceramic material to fabricate 3D white graphene (WG) foams without using any catalysts or templates for superstrong pollutant removal applications. Importantly, the introduction of vesicants guaranteed the reproducibility and yield (4500 cm 3 ). Interestingly, these 3D WG foams possessed a vesicular structure with hierarchical pores ranging from nm to μm scales and with ultrathin walls consisting of mono-or few-layered BN membranes with planar sizes as large as 100 μm. Consequently, such microstructure merits of hierarchical pores and ultrathin walls endowed them not only very low density (2.1 mg cm − 3 ) but also superstrong adsorption ability, illustrated by capacitances up to 190 times its own weight toward a wide range of environment contaminations, including various oils and dyes. Thus, the 3D h-BN WG foams prepared by vesicant-assisted foaming should have great potential as outstanding environmental scavengers. NPG Asia Materials (2015) 7, e168; doi:10.1038/am.2015.8; published online 27 March 2015 INTRODUCTION Two-dimensional (2D) crystals, such as graphene 1 and white graphene (WG, mono-or few-layered hexagonal boron nitride (h-BN)), 2,3 have triggered great interest because of their extraordinary intrinsic properties and wide range of applications in electronics, optoelectronics, energy storage and the environment. 4 However, for some specific applications, such as the adsorption of various contaminants and as electrodes in electrochemical cells, their pristine flat 2D structures have been recognized to not fully match the practical requirements. [5][6][7][8] In contrast, three-dimensional (3D) architectures using 2D crystals as building blocks can simultaneously provide the virtues of 2D and 3D structures, such as ultrathin sheets and large specific surface areas from 2D sheets 6 and hierarchical pores and ultralight densities from 3D configurations. 7 Recently, such novel 2D-3D structure features have been proven to exhibit new and outstanding performances. For instance, graphenecarbon nanotube 3D structures had densities as low as 0.16 mg cm − 3 , even lighter than air (1.29 mg cm − 3 ); 9 3D graphene and BN networks exhibited excellent mechanical properties; 10,11 3D BNC hybrid networks showed tunable electronic and thermal properties. 12 However, the high-yield fabrication of such 3D architectures of 2D crystals, especially without using any templates or catalysts, remains a great challenge. Currently, there are two methods for fabricating 3D

Fabrication of Hexagonal Boron Nitride Nanosheets by Using a Simple Thermal Exfoliation Process

“…In the FT-IR spectrum shown in Figure 6(a), only two peaks centered at 1381 cm -1 and 815 cm -1 can be observed, assigned to in-plane B-N stretching (in-plane ring vibration, the E 1u mode) and B-N bending (out-of-plane vibration, A 2u mode), respectively. 16 In Fig. 6(b) BNNSs though the thermal exfoliation process are pure phase h-BN products without any oxidation or functionalization of the BNNSs.…”

Boron Nitride Nanostructures: Fabrication, Functionalization and Applications

“…Heating mixture of melamine and boric acid at 1000 °C in an ammonia atmosphere can remove the carbonaceous composition, and the obtained h‐BN porous material shows the highest specific surface area ever reported for any BN system, up to 1488 m 2 g −1 , and outstanding hydrogen storage performance . Introducing thiourea as vesicant into the ammonia borane source can improve the reproducibility and yield of 3D h‐BN foams, and the obtained foams possess a vesicular structure with hierarchical pores and ultrathin walls …”

Tunable porous boron nitride: Investigating its formation and its application for gas adsorption

“…Recent studies have reported the use of porous BN for gas phase and liquid phase adsorption. The focus has mostly been on CO 2 capture [4][5][6], H 2 storage [7][8][9][10], pollutants removal from air [11,12], water pollutants removal [7,[12][13][14][15][16][17][18][19][20][21][22] and oil adsorption [15,21,22]. For instance, recent work by Nag et al [5] reported the synthesis of boron nitride with a CO 2 adsorption capacity of up to 32 wt.…”

“…% at 195 K and 0.85 P/P o . Furthermore, it was demonstrated by Zhao et al that boron nitride 3D foam could adsorb between 70 and 190 times its weight in organic pollutants and oils [22].…”