Synthesis and comparative evaluation of optical and electrochemical properties of efficacious heterostructured-nanocatalysts of ZnSe with commercial and reduced titania

Highlights: • Solvothermal synthesis of semiconductor-semiconductor (S-S) type heterostructures of ZnSe and TiO₂. • Defects and heterostructure architecture increases the carrier's life time and visible light response of titania. • Ultrafast electrochemical kinetics for overall water splitting by heterostructures in comparison with commercial titania. • The heterostructures with cascade bandgap alignment manifest efficient photocatalytic degradation of RB-866 dye. -- Abstract: We report semiconductor-semiconductor (S-S) type heterostructures prepared by solvothermal method using ZnSe (Z), commercial titania (C-TiO₂) and reduced titania (R-TiO_2−x) as precursor materials. The synthesized Z-C-TiO₂ and Z-R-TiO_2−x heterostructures manifest remarkable electrocatalytic oxygen evolution reaction (OER) activity with onset over potential of only 320 mV (Tafel slope = 40 mV dec⁻¹) and 325 mV (Tafel slope = 45 mV dec⁻¹) respectively, with activity over 6 h of testing time in alkaline medium. This enhancement in the activities of engineered nanoscale materials can be attributed to the better coping of reaction intermediate through synergistic effect of two semiconducting materials. Owning to the reduced electron-hole recombination by versatile cascade band alignment of titania with ZnSe, these heterostructures also show superior photocatalytic activity for degradation of reactive blue-866 dye (RB-866) under visible light irradiation when compared to pure titania.