The undesirable influences of hazardous pollutants on the environment and the global demand for using renewable and environmentally clean energy sources necessitate the development of appropriate ways for controlling environmental pollution and also energy challenges. In this research, a square planar Ni (II) complex, [Ni(DMSO)₂(QA)₂](NO₃)₂, where QA = quinacridone, was synthesized and characterized. Afterward, the complex was exploited as an electrocatalyst for hydrogen evolution reaction (HER) in acidic media. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were applied to investigate the electrocatalytic properties of the Ni(II) complex toward the HER process. The overpotential and Tafel slope of the Ni(II) complex are 229 mV at 10 mA cm⁻² and 76 mV dec⁻¹, respectively. The Ni(II) complex is favored for its fast HER kinetics, proper durability, and low price. In addition, the Ni (II) complex was used as a photocatalyst in the photodegradation reaction of acridine orange (AO) under visible light at different pH values in H₂O. The photocatalytic reaction progress was monitored by UV–Vis spectroscopy. Compared to the free QA ligand, the Ni(II) complex exhibited high efficiency in the photocatalytic reactions, and more than 96% of AO dye was degraded under the optimized conditions at 180 min. A small band gap, efficient light-harvesting capability, easy separation, adequate recyclability, and simple synthesis route make the prepared Ni(II) complex an eco-friendly and efficient photocatalyst for photocatalytic degradation reactions under visible light irradiation.

Keywords: Ni(II) complex Quinacridone Hydrogen evolution reaction Acridine orange Photocatalyst Electrocatalyst