Comparison between Base Metals and Platinum Group Metals in Nitrogen, M Codoped TiO₂ (M = Fe, Cu, Pd, Os) for Photocatalytic Removal of an Organic Dye in Water

Table 2

Optical band gaps of the materials.

Sample	Optical band gap (eV)
Comm. TiO2 (P25)	3.1
N TiO2	2.7
N, Pd TiO2	2.1
N, Fe TiO2	2.6
N, Os TiO2	2.0
N, Cu TiO2	2.8