Gas-Exfoliation Assisted Fabrication of Porous Graphene Nanosheets Derived from <i>Plumeria rubra</i> for Highly Efficient Photocatalytic Hydrogen Evolution

Abstract

An environmentally friendly strategy was performed to prepare porous graphene nanosheets (PGS) through gas-exfoliation assisted KOH activation by using Plumeria rubra as the precursor for the first time. Because the synergistic reaction of various graphitization temperature and activating agent amounts, the precursor was gradually exfoliated by released gases, graphitizing at high temperatures and forming porous graphene nanosheets during the graphitization. PGS-2-1000 with a hierarchical porous structure possessed high graphitization (ID/IG = 0.77, I2D/IG = 0.53), ultrahigh specific surface (1581 m2 g–1) and large pore volume (0.916 cm3 g–1). A facile in situ photoreduction treatment was utilized to form a Cu/PGS photocatalyst composed of nonsemiconductor plasmonic Cu NPs and porous graphene nanosheets, exhibiting the hydrogen evolution rate of 4.87 mmol g–1 h–1, which is 4-fold as high as that of single Cu NPs. The photostability of Cu/PGS-2-1000 was investigated in five consecutive runs of 30 h accumulative irradiation. The PGS could act as an electron transport bridge to boost the separation of electron–hole pairs and the uniform distribution of Cu NPs, even serve as a photocatalyst for hydrogen generation. Furthermore, a possible mechanism was proposed to illustrate the circumstantial charge transfer channel as well as the improvement of photocatalytic activity.