Investigating the effect of Nd3+ dopant and the formation of g-C3N4/BiOI heterostructure on the microstructural, optical and photoelectrocatalytic properties of g-C3N4

A two-step thermal poly-condensation and hydrothermal method is used to prepare noble metal-free nano-heterostructure of neodymium (Nd)-doped graphitic carbon nitride (g-C3N4) and bismuth oxyiodide (BiOI). The synthesised Nd- doped g-C3N4/BiOI heterostructure shows high electron-hole separation. Moreover, a fast charge transport at the heterojunction is noted and further leads to low charge recombination rate. Consequently, the synthesised heterostructure overcomes the high charge recombination rate of g-C3N4. This work reports the effect of Nd- doping and the formed heterojunction on the structural, optical, electrical conductivity and photoelectrochemical (PEC) properties of the heterostructure. Moreover, introducing Nd dopant into g-C3N4 enhances visible light absorption of g-C3N4. The optimal hetero-nanostructure (5.0 wt% Nd doped g-C3N4/BiOI) shows high photocurrent density (15.50 mA/cm2) and hydrogen evolution rate (288 mu mol h-1 cm-2) under visible light (lambda >= 420 nm) illumination when compared to other wt.% of Nd doped g-C3N4 and heterostructure. Additionally, the low emission features obtained from the photoluminescence studies and the heterojunction visually observed by HRTEM strongly emphasise that the formation of heterostructure leads to low recombination of charge carriers. Doping and forming heterostructure is shown to be an effective, controllable and an optimal approach to improve the PEC water splitting performance of g-C3N4.