Enhanced Photo/Electrocatalytic Hydrogen Evolution by Hydrothermally Derived Cu-Doped TiO2 Solid Solution Nanostructures

Highly efficient nanocatalysts with a high specific surface area were successfully synthesized by a cost-effective and environmentally friendly hydrothermal method. Structural and elemental purity, size, morphology, specific surface area, and band gap of pristine and 1 to 5% Cu-doped TiO₂ nanoparticles were characterized by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), energy dispersive X-ray analysis (EDAX), inductively coupled plasma mass spectrometry (ICP-MS), liquid chromatography-high resolution mass spectrometry (LC-HRMS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET surface area, Raman spectroscopy, photoluminescence spectroscopy (PL) and UV-visible diffused reflectance spectroscopy (UV-DRS) studies. The XPS and EPR findings indicated the successful integration of Cu ions into the TiO₂ lattice. UV-DRS and BET surface area investigations revealed that with an increase in dopant concentration, Cu-doped TiO₂ NPs show a decrease in band gap (3.19-3.08 eV) and an increase in specific surface area (169.9-188.2 m²/g). Among all compositions, 2.5% Cu-doped TiO₂ has shown significant H₂ evolution with an apparent quantum yield of 17.67%. Furthermore, the electrochemical water-splitting study shows that 5% Cu-doped TiO₂ NPs have superiority over pristine TiO₂ for H₂ evolution reaction. It was thus revealed that the band gap tuning with the desired dopant concentration led to enhanced photo/electrocatalytic sustainable energy applications.