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 (>500 cm3). 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. Vesicant-induced foaming has been used to produce three-dimensional white graphite foams with very high adsorption capacities. Researchers based in Nanjing, China, fabricated these foams of white graphite (i.e., mono- or few-layered hexagonal boron nitride) by using a vesicant to release a gas during the fabrication of hexagonal boron nitride. The resulting foams had a vesicular structure with pores ranging in size from several nanometres to several hundred micrometres. This structure endowed them with both a very low density (2.1 mg cm-1) and an extremely absorption capacity — up to 190 times their own weight for a wide range of environmental contaminants — making them highly attractive as pollutant scavengers for water treatment. The fabrication method is straightforward and readily scalable and is thus amenable for industrial production. A vesicant-assisted gas-foaming strategy has been reported to achieve 3D h-BN white graphene (WG) foams without any catalysts or templates. This technique could provide large-scale, high-yield and ultralight 3D WG foams with a very low density of 2.1 mg cm−3. The WG foams present hierarchical pores and ultrathin walls with single or several atomic layers. The WG foams present superhigh adsorption properties for organic solvents and oils with an adsorption capacity of up to 70–190 times its own weight for organic pollutants and oils. This study promotes a new design strategy to create 3D WG foams for high-performance pollutant removal applications in water treatment.