Nitrogen Graphene: A New and Exciting Generation of Visible Light Driven Photocatalyst and Energy Storage Application

The synthesis of nitrogen, boron, and nitrogen-boron-codoped graphenes was attained via mixing solutions of GO with urea, boric acid, and a mixture of both, respectively, followed by drying in vacuum and annealing at 900 °C for 10 h. These materials were thoroughly characterized employing XRD, TEM, FTIR, Raman, UV-vis, XPS, IPCE%, and electrical conductivity measurements. The nitrogen-doped graphene (NG) showed an excellent supercapacitor performance with a higher specific capacitance (388 F·g^-1 at 1 A·g^-1), superior stability, and a higher power density of 0.260 kW kg^-1. This was mainly due to the designated N types of doping and most importantly N-O bonds and to lowering charge transfer and equivalent series resistances. The NG also indicated the highest photocatalytic performance for methylene blue (MB 20 ppm, power = 160 W, λ > 420 nm) and phenol (5 ppm) degradation under visible light illumination with rate constants equal 0.013 min^-1 and 0.04 min^-1, respectively. The photodegradation mechanism was proposed via determining the energy band potentials using the Mott-Schottky measurements. This determined that photoactivity enhancement of the NG is accounted for by acquisition of nitrogen-oxy-carbide phases that shared in inducing a higher IPCE% (60%) and a lower band gap value (1.68 eV) compared to boron and nitrogen-boron-codoped graphenes. The achieved photodegradation mechanism relied on scavengers performance suggesting that ^•OH and electrons were the main reactive species responsible for the MB photodegradation.