Band structure and photoelectrochemical behavior of AgNbO3–NaNbO3 solid solution photoelectrodes

NaNbO3, (AgNbO3)0.5(NaNbO3)0.5 and AgNbO3 films on FTO conducting glass substrates were fabricated by pulsed laser deposition at 973 K for 1 h under 10 Pa oxygen pressure with the laser energy of 400 mJ. The energy band structure and photoelectrochemical behavior were investigated by measuring the flatband potential (Vfb) and photocurrent. The optical band gaps for NaNbO3, (AgNbO3)0.5(NaNbO3)0.5 and AgNbO3 are 3.50, 3.25 and 2.93 eV, respectively. And the Vfb for the NaNbO3, (AgNbO3)0.5(NaNbO3)0.5 and AgNbO3 films are −0.91, −0.76 and −0.88 V (vs. Ag/AgCl), respectively, indicating that the conduction band bottom of (AgNbO3)0.5(NaNbO3)0.5 is more positive than those of NaNbO3 and AgNbO3, and the valence band top becomes more positive in order of AgNbO3, (AgNbO3)0.5(NaNbO3)0.5 and NaNbO3. The AgNbO3 film shows the largest photocurrent density due to the more light harvesting, the relative higher donor density and large contact surface area between the electrode and the electrolyte solution. The (AgNbO3)0.5(NaNbO3)0.5 film shows lowest photocurrent due to lower donor density.