Photocatalysts of Na1-xLaxTa1-xCrxO3 and NaTa1-xCrxO3 were prepared by spray pyrolysis from aqueous and polymeric precursor solution. Apart from the contribution of La3+ ions co-doped into NaTa1-xCrxO3 on the BET surface area and the surface morphology by preventing crystal growth, this co-doping contributed to the increased Cr3+ concentration by partially tuning the electron configuration from A(+)B(5+)O(3) to (A(+)A'(3+))(2+)(B5+B'(3+))O-4+(3) in the lattice of the photocatalyst. Na1-xLaxTa1-xCrxO3 prepared from polymeric precursor solution reduced the induction period to 33% and enhanced the hydrogen evolution rate 5.6-fold to 1467.5 mu mol g(-1) h(-1) compared with the equivalent values of NaTa1-xCrxO3 prepared from aqueous precursor. The optimum amounts of dopant and additives comprising the polymeric precursor to maximize the hydrogen evolution rate were x = 0.003 and 300 mol%, respectively. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.