Synergistic effect of oxygen vacancies and built-in electric field in GdCrO3/BiVO4 composites for boosted photocatalytic reduction of nitrate in water

As a promising approach for nitrate nitrogen removal in water, photocatalysis required sufficient photogenerated charges to achieve a high photocatalytic efficiency. Herein, a novel GdCrO3/BiVO4 composite was prepared by the solid-state combustion method combined with hydrothermal treatment. The synergistic effect of oxygen vacancies introduced by chemical reduction method and built-in electric field formed in GdCrO3/BiVO4 heter-ostructures suppressed the charge recombination, which eventually improved the photocatalytic activity. Effects of photocatalyst composition, HCOOH dosage and oxygen vacancy concentration on photocatalytic activity were investigated. It was found that 0.30-GdBiOVs composites exhibited highest photocatalytic activity with nitrate removal ratio of 97.05% and N2 selectivity of 92.76% in 40 min. Moreover, end-products of nitrate nitrogen elimination and stability of photocatalysts were revealed. The existences of oxygen vacancies and built-in electric field were confirmed by EPR and HRTEM analyses. Ultimately, the possible mechanisms of nitrate nitrogen elimination were clarified.