Preparation and Property Characterization of Eu2SmSbO7/ZnBiEuO4 Heterojunction Photocatalysts and Photocatalytic Degradation of Chlorpyrifos under Visible Light Irradiation

Eu2SmSbO7 and ZnBiEuO4 were synthesized for the first time using the hydrothermal method. Eu2SmSbO7/ZnBiEuO4 heterojunction photocatalyst (EZHP) was synthesized for the first time using the solvothermal method. The crystal cell parameter of Eu2SmSbO7 was 10.5547 Å. The band gap width of Eu2SmSbO7 was measured and found to be 2.881 eV. The band gap width of ZnBiEuO4 was measured and found to be 2.571 eV. EZHP efficiently degraded the pesticide chlorpyrifos under visible light irradiation (VLID). After VLID of 160 min, the conversion rate of the chlorpyrifos concentration reached 100%, while the conversion rate of the total organic carbon (TOC) concentration was 98.02% using EZHP. After VLID of 160 min, the photocatalytic degradation conversion rates of chlorpyrifos using EZHP were 1.13 times, 1.19 times, and 2.84 times those using Eu2SmSbO7, ZnBiEuO4, and nitrogen-doped titanium dioxide (N-doped TiO2), respectively. The photocatalytic activity could be ranked as follows: EZHP > Eu2SmSbO7 > ZnBiEuO4 > N-doped TiO2. The conversion rates of chlorpyrifos were 98.16%, 97.03%, 96.03%, and 95.06% for four cycles of experiments after VLID of 160 min using EZHP. This indicated that EZHP was stable and could be reused. In addition, the experiments with the addition of capture agents demonstrated that the oxidation removal ability of three oxidation free radicals for degrading chlorpyrifos obeyed the following order: hydroxyl radical > superoxide anion > holes. This study examined the intermediates of chlorpyrifos during the photocatalytic degradation of chlorpyrifos, and a degradation path was proposed, at the same time, the degradation mechanism of chlorpyrifos was revealed. This study provides a scientific basis for the development of efficient heterojunction photocatalysts.