Bottom-up synthesis of semiconductive carbonaceous nanosheets on hematite photoanode for photoelectrochemical water splitting

Coupling two-dimention carbon materials like graphene on photodelectrode can achieve high-efficiency photoelectrochemical cells.Bottom-up synthesis of carbon-based two-dimensional materials in green media from simple molecules is very attractive but remains a challenge.Carbohydrate is an ideal precursor for the synthesis but previous report requires pyrolysis at high temperature(>700℃).Herein,starting with glucose,we develop a low temperature(210℃)synthesis of carbonaceous nanosheets in aqueous solution of glucose.With the aid of ethylenediamine and Fe3+/Fe27Co27Ni2+ions,the nanosheets can grow on hematite nanorod array with very close contact.Importantly,a metallic region is formed at the interface due to atom distribution distortion,which can promote the charge transfer.The activity can be greatly enhanced by about 500%due to fast charge transfer.This is much better than that prepared by physically or chemically mixing graphene and hematite(<200%).The enhancement is mainly due to the deformation area between the nanosheets and the hematite.The effective hole diffusion length increases from 2 to 8 nm and lifetime of charge carrier also increases,as confirmed by ultrafast transient absorption spectra.This method provides more opportunity for simple,mild and cost-effective fabrication of carbon-based two-dimensional by bottom-up method.