UV/vis spectroscopic and x-ray photoelectron spectroscopic data of photocatalytic chromium oxide impregnated niobium oxide. UV/vis diffuse reflectance data collected using a Perkin-Elmer Lambda 650 S UV/vis spectrometer equipped with a Labsphere integrating sphere over the spectral range 190-900 nm, using BaSO4 reflectance standards. X-ray photoelectron spectroscopy (XPS) was carried out on a Scienta ESCA 300 spectrometer located at the NCESS facility at Daresbury Laboratory, UK, which incorporated a rotating anode Al Kα (hv = 1486.6 eV) X-ray source and had an effective instrument resolution of 400 meV. The spectrometer was calibrated regularly to set the Fermi edge of a silver reference sample at zero binging energy. Sample charging was compensated for using an electron flood gun. The binding energy scale was referenced using the adventitious carbon C1s peak which was set to 284.6 eV.