Chemical blowing strategy for three-dimensional graphene materials: Overcoming graphene restacking and integrating macro/microstructural construction

Abstract

Carbon materials, characterized by diverse allotropes, have played critical roles in the advancement of human civilization and industrial manufacturing. As a prominent allotrope, two-dimensional (2D) graphene materials have attracted increasing attention since their discovery owing to their exceptional properties; however, they suffer from the fundamental challenges of restacking and agglomeration, which diminish their performance in practical applications. The design of three-dimensional (3D) frameworks composed of 2D graphene sheets is considered an effective strategy to resolve these issues and enable the efficient utilization of the properties of graphene. Compared with conventional fabrication methods, such as graphene oxide assembly and template-assisted chemical vapor deposition, the chemical blowing strategy is distinguished by its low cost, facile process, and superior controllability. Despite these advantages, few review articles have focused specifically on the fabrication of 3D graphene materials via chemical blowing. This review outlines the chemical blowing strategy and clarifies the fundamentals of the blowing process, its historical evolution, and the classification of 3D graphene materials. Subsequently, the recent progress in 3D graphene foams and powders fabricated via chemical blowing is detailed, with an emphasis on the underlying synthesis chemistry. Following an analysis of the correlation between 3D graphene foam and powder materials, their design considerations and functional applications are discussed. This discussion provides recommendations for the synthesis of specific 3D graphene materials and elucidates their differences and commonalities across various application scenarios. Finally, after a brief summary, current challenges, opportunities, and future research directions for the development of chemical blowing are proposed.

1. Introduction

As one of the most widely distributed elements on Earth, carbon is indispensable for the natural biomass cycle as well as the advancement human civilization and industrial manufacturing. Due to its unique electronic structure, carbon reacts with numerous other elements to form a vast array of organic and inorganic non-metallic compounds. Furthermore, carbon can form various allotropes with unique structures and exceptional characteristics through sp2/sp3 electron orbital hybridization, such as the zero-dimensional (0D) fullerene, one-dimensional (1D) carbon nanotubes (CNTs), and the prominent two-dimensional (2D) graphene. Graphene, as a constituent unit of graphite, has garnered unprecedented research attention since its initial discovery via mechanical exfoliation by Novoselov et al. in 2004. Graphene sheets, which consist of a honeycomb-like network of sp2-hybridized carbon atoms in a single plane, is the thinnest material known to possess extraordinary properties. These include exceptional electrical conductivity (~150000 cm2·V–1·s–1), high thermal conductivity (~5000 W·m–1·K–1), high specific surface area (SSA, ~2630 m2·g–1), high mechanical strength, and superior chemical stability. Consequently, the 2010 Nobel Prize in Physics was awarded to Geim and Novoselov for the groundbreaking discovery of graphene. Within this context, an increasing number of research topics concerning graphene have been reported over the past two decades, fostering the growth of graphene-based studies in the fields of chemistry and materials science. This has led to the exploration of diverse new synthetic strategies and various application scenarios for graphene materials.

However, in terms of practical applications, 2D graphene sheets tend to restack and further transform into graphite microsheets (Fig. 1(a)) due to the inherent π–π bonding and van der Waals forces between graphene layers. This transformation results in the loss of the fascinating properties of graphene. Constructing well-organized and interconnected three-dimensional (3D) frameworks composed of 2D sheets has been proposed as an effective strategy to address this issue. Such frameworks can maintain the excellent properties of the 2D graphene sheets while expanding the application scenarios without the limitations of restacking (Fig. 1(b)). Based on this concept, a substantial number of scientific studies on 3D graphene materials have been published, focusing primarily on macroscopic 3D graphene hydrogels, foams, sponges, and microscopic 3D graphene powder [16‒20].