Effect of boron doping level on the photocatalytic activity of graphene aerogels

Heteroatom-doped three-dimensional (3D) graphene-based macroscopic assemblies (GMAs) are receiving considerable attention for application as heterogeneous photocatalysts. However, the relationship between the concentration and the bonding state of heteroatoms at the atomic scale and the resulting photoelectronic and photocatalytic properties of 3D GMAs remain unexplored. Herein, we describe a simple, environmentally benign, one-pot hydrothermal reduction-induced self-assembly process to prepare boron-doped graphene aerogels by using graphene oxide and boric acid as carbon (C) and boron (B) sources, respectively. By rationally adjusting the dopant elemental precursor, the B content was modulated from ∼0.14 to ∼3.37 at%. The as-synthesized B-doped bulk graphene monoliths with well-defined interconnected 3D porous networks can effectively degrade acridine orange (AO), a well-known recalcitrant and biologically toxic pollutant, under visible light irradiation. Particularly, the aerogel with a moderate B loading of ∼2.15 at% displayed a superior photodegradation efficiency of ∼98%, which is 2.13 times higher than the undoped material. The generation of oxygenated B derivatives, such as borinic esters and boronic acids, on the edge sites and defect regions of the 2D graphene building blocks was primarily responsible for the exceptional photocatalytic activity. Besides, these macroscale photocatalysts are highly stable and easily recyclable for practical applications.