Electroless Ni plated nanostructured TiO₂ as a photocatalyst for solar hydrogen production

Herein, we have demonstrated a facile electroless Ni coated nanostructured TiO₂ photocatalyst for the first time. More significantly the photocatalytic water splitting shows excellent performance for hydrogen production which is hitherto unattempted. The structural study exhibits majorly the anatase phase along with the minor rutile phase of TiO₂. Interestingly, electroless nickel deposited on the TiO₂ nanoparticles of size 20 nm shows a cubic structure with nanometer scale Ni coating (1-2 nm). XPS supports the existence of Ni without any oxygen impurity. The FTIR and Raman studies support the formation of TiO₂ phases without any other impurities. The optical study shows a red shift in the band gap due to optimum nickel loading. The emission spectra show variation in the intensity of the peaks with Ni concentration. The vacancy defects are pronounced in lower concentrations of Ni loading which shows the formation of a huge number of charge carriers. The electroless Ni loaded TiO₂ has been used as a photocatalyst for water splitting under solar light. The primary results manifest that the hydrogen evolution of electroless Ni plated TiO₂ is 3.5 times higher (1600 μmol g^-1 h^-1) than pristine TiO₂ (470 μmol g^-1 h^-1). As shown in the TEM images, nickel is completely electroless plated on the TiO₂ surface, which accelerates the fast transport of electrons to the surface. It suppresses the electron-hole recombination drastically which is responsible for higher hydrogen evolution using electroless Ni plated TiO₂. The recycling study exhibits a similar amount of hydrogen evolution at similar conditions which shows the stability of the Ni loaded sample. Interestingly, Ni powder loaded TiO₂ did not show any hydrogen evolution. Hence, the approach of electroless plating of nickel over the semiconductor surface will have potential as a good photocatalyst for hydrogen evolution.