Porous structure dependent photoreactivity of graphitic carbon nitride under visible light

We demonstrate that graphitic carbon nitride can photoreduce CO2 to CO in the presence of water vapor and exhibit interesting porous structure dependent reactivity on photoreduction and photooxidation under visible light (lambda > 420 nm). Graphitic carbon nitride was synthesized by directly heating the inexpensive melamine and the replacement of melamine with melamine hydrochloride could result in porousification in the final graphitic carbon nitride with much higher surface area (39 times) and more abundant pores, accompanied by a band gap increase of 0.13 eV. The porousification could significantly enhance the photoreactivity of graphitic carbon nitride in rhodamine B photooxidation by 9.4 times, but lower its activity in CO2 photoreduction by 4.6 times. The reasons for the porous structure dependent photoreactivity were investigated in detail. These new findings could shed light on the design of efficient photocatalysts and the tuning of their photoreactivity for environmental and energy applications.