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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. Full article

An unprecedented photocatalyst, Sm₂EuSbO₇, was successfully fabricated in this paper, through a high-temperature solid-state calcination method, which represented its first ever synthesis. Additionally, using the solvothermal method, the Sm₂EuSbO₇/ZnBiSbO₅ heterojunction photocatalyst (SZHP) was fabricated, marking its debut in this study. XRD analysis confirmed that both Sm₂EuSbO₇ and ZnBiSbO₅ exhibited pyrochlore-type crystal structures with a cubic lattice, belonging to the Fd3m space group. The crystal cell parameter was determined to be 10.5682 Å or 10.2943 Å for Sm₂EuSbO₇ or ZnBiSbO₅, respectively. The band gap width measured for Sm₂EuSbO₇ or ZnBiSbO₅ was 2.73 eV or 2.61 eV, respectively. Under visible light irradiation for 150 min (VLTI-150 min), SZHP exhibited remarkable photocatalytic activity, achieving 100% removal of parathion methyl (PM) concentration and 99.45% removal of total organic carbon (TOC) concentration. The kinetic constant (k) for PM degradation and visible light illumination treatment was determined to be 0.0206 min⁻¹, with a similar constant k of 0.0202 min⁻¹ observed for TOC degradation. Remarkably, SZHP exhibited superior PM removal rates compared with Sm₂EuSbO₇, ZnBiSbO₅, or N-doped TiO₂ photocatalyst, accompanied by removal rates 1.09 times, 1.20 times, or 2.38 times higher, respectively. Furthermore, the study investigated the oxidizing capability of free radicals through the use of trapping agents. The results showed that hydroxyl radicals had the strongest oxidative capability, followed by superoxide anions and holes. These findings provide a solid scientific foundation for future research and development of efficient heterojunction compound catalysts. Full article