Here we report improved photocatalytic activity of ZnO nanostructures through judicious choice of the dopant, particularly by choosing the dopant with high chemical hardness. We have doped ZnO nanostructures with divalent (Ni²⁺ and Sr²⁺) and trivalent (Cr³⁺ and Al³⁺) using hydrothermal conditions. The photocatalytic activity of undoped and doped ZnO nanostructures was tested towards the degradation of methyl orange (MO), methylene blue (MB), and congo red (CR). The Al-ZnO exhibited a 91.25% removal rate compared to 40.88% for pure ZnO in MO degradation under ultraviolet (UV) radiation. The trend of photocatalytic activity of different photocatalysts (Al-ZnO > Sr-ZnO > Cr-ZnO > Ni-ZnO > ZnO) is similar to the trend of Pearson hardness values of Al³⁺ > Sr²⁺ > Cr³⁺ > Ni²⁺ > Zn²⁺. These reactions also reveal that the dopant type affects the morphology of the ZnO nanostructures in given reaction conditions. We propose the polarity-induced mechanism to understand the changes in the morphology due to different dopants.

在这里，我们报告了通过明智地选择掺杂剂，特别是通过选择具有高化学硬度的掺杂剂来提高 ZnO 纳米结构的光催化活性。我们掺杂了二价（Ni ²⁺和 Sr ²⁺）和三价（Cr ³⁺和 Al ³⁺）的ZnO 纳米结构) 使用热液条件。测试了未掺杂和掺杂的 ZnO 纳米结构对甲基橙 (MO)、亚甲蓝 (MB) 和刚果红 (CR) 降解的光催化活性。在紫外 (UV) 辐射下的 MO 降解中，Al-ZnO 表现出 91.25% 的去除率，而纯 ZnO 的去除率为 40.88%。不同光催化剂（Al-ZnO > Sr-ZnO > Cr-ZnO > Ni-ZnO > ZnO）的光催化活性变化趋势与Al ³⁺  > Sr ²⁺  > Cr ³⁺ > Ni皮尔逊硬度值变化趋势相似²⁺  > 锌²⁺. 这些反应还表明，在给定的反应条件下，掺杂剂类型会影响 ZnO 纳米结构的形态。我们提出了极性诱导机制来理解由于不同掺杂剂引起的形态变化。