Superfast microwave synthesis of hierarchically porous rGO by graphite ignited reduction propagation

Hierarchically porous graphene materials have great potential for applications in energy storage, electrocatalysis, water treatment, etc. Herein, a simple, superfast and effective approach was developed to hierarchically porous graphene with both micron-scale inter-layer pores and nanoscale in-plane holes, where a small amount of graphite acted as microwave absorbent to ignite a so-called reduction propagation process and the first reduced graphene oxide (rGO) acted as new igniter to reduce all the surrounding graphene oxide (GO). It was found that the porous structure and degree of reduction of hierarchically porous rGO could be tailored simply by controlling the microwave irradiation time and power. GO was completely reduced in 5 s of microwave irradiation. When the irradiation time was further extended, more crystalline graphitic domains formed on the rGO, and the number of in-plane holes, which were rare in more shortly irradiated specimens, increased significantly after more than 40 s microwave irradiation. The relationship between these physicochemical characteristics of the obtained hierarchically porous rGO and the microwave irradiation conditions is discussed in detail in this paper, which has great significance in designing hierarchically porous graphene materials required for supercapacitor electrodes, electrocatalysts, and water-treatment membranes.