H2 evolution under visible light irradiation on La and Cr co-doped NaTaO3 prepared by spray pyrolysis from polymeric precursor

• Na1−xLaxTa1−xCrxO3 was prepared by spray pyrolysis from polymeric precursor.
• La3+ ion contributed on the BET surface area and the surface morphology.
• La3+ ion increased Cr3+ by tuning the structure to (A+A′3+)2+(B5+B′3+)4+O3.
• Cr3+ positively but Cr6+ negatively affects the hydrogen evolution rate.

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+B5+O3 to (A+A′3+)2+(B5+B′3+)4+O3 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 μmol 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.