Nickel incorporated graphitic carbon nitride supported copper sulfide for efficient noble-metal-free photo-electrochemical water splitting

Solar hydrogen generation through photo-electrochemical (PEC) water splitting is potential technology but equally challenging to address the growing energy demand as well as the concerns related to the use of fossil fuels, and several strategies have been devised to address these concerns. Herein, we report a nanohybrids of copper sulfides supported on nickel-incorporated graphitic carbon nitride (Ni/g-C3N4@CuS) sheets for enhanced activity towards PEC water oxidation. The TEM images confirm the presence of intimate contact between nickel doped graphitic carbon nitride and CuS, forming an interface which is favorable for an effective separation of charge-carriers. The electrochemical properties of the prepared samples are investigated through linear sweep voltammetry, electrochemical impedance spectroscopy, Mott-Schottky analysis, and chopped photo-current measurements. The Ni/g-C3N4@CuS nanohybrids depicts almost three-fold enhancement in current density under light illumination reaching to 15.5 mA cm−2 at an over potential of ca. 600 mV than in the dark and almost fifteen-fold enhancement as compared to its parent materials, CuS and g-C3N4. The enhanced activity towards PEC water splitting is assigned to the larger extent of band bending as illustrated by larger space charge region width, formation of p-n junction between CuS and g-C3N4, lowering of effective band gap of the resulting hetero-structures, and facile charge transfer kinetics due to Ni-incorporation into the g-C3N4 matrix.