Transition metal/metal ions are reported to impart very efficient co-catalytic activity to TiO₂ for various photocatalytic reactions depending on the nature and oxidation state of metal ions. However, when certain metals (Mⁿ⁺) having different oxidation states like Mn²⁺/Mn⁷⁺ or Cr³⁺/Cr⁶⁺ act as co-catalysts, the photocatalytic properties of Mⁿ⁺-TiO₂ nanocomposites may vary significantly. Different surface morphologies, electron transfer phenomena and adsorption efficacy provided by these co-catalysts will govern the Mⁿ⁺-TiO₂ photoactivity. In this context, this paper demonstrates the preparation and characterization of Mn²⁺/Mn⁷⁺-TiO₂ nanocomposites for investigating the above physicochemical properties for the degradation of toxic herbicide Methyl viologen under sunlight irradiation. The optical spectra of these catalysts showed bathochromic shifts (from 355 to 572 nm) due to the presence of Mn²⁺ and Mn⁷⁺ ions. The higher co-catalyst stability, smaller D_max (maximum average diameter) and mixed morphological characteristics have been illustrated by SAXS and TEM analysis with size range ∼ 25–30 and 20−35 nm for Mn²⁺-TiO₂ and Mn⁷⁺-TiO₂ nanocomposites, respectively. The adsorption-desorption studies using NH₃ gas revealed that Mn⁷⁺ ions generate enhanced Lewis acidity on the co-catalyst surface compared to Mn²⁺ impregnations. The best fit for Freundlich adsorption isotherm (K_f = 23.44 μg/mg) was possessed by Mn⁷⁺-TiO₂ than Mn²⁺-TiO₂ and TiO₂ photocatalyst confirming its higher substrate affinity and photodegradation efficiency. The Mn²⁺ and Mn⁷⁺ impregnations displayed 2.6 and 3.7 times higher photoactivity than bare TiO₂ which has been correlated to different oxidation states and surface structural properties imparted by Mnⁿ⁺ ions.

据报道，根据金属离子的性质和氧化态，对于各种光催化反应，过渡金属/金属离子可赋予TiO ₂非常有效的助催化活性。但是，当某些具有不同氧化态的金属（M ^{n +}）像Mn ²⁺ / Mn ⁷⁺或Cr ³⁺ / Cr ⁶⁺充当助催化剂时，M ^{n +} -TiO ₂纳米复合材料的光催化性能可能会发生显着变化。这些助催化剂提供的不同表面形态，电子转移现象和吸附效率将决定M ^{n +} -TiO ₂光活性。在此背景下，本文证明了Mn ²⁺ / Mn ⁷⁺ -TiO ₂纳米复合材料的制备和表征，以研究上述理化性质对日光照射下有毒除草剂甲基紫精的降解作用。由于存在Mn ²⁺和Mn ⁷⁺离子，这些催化剂的光谱显示出红移（从355 nm到572 nm）。通过SAXS和TEM分析，在Mn ²⁺ -TiO ₂和Mn ^7+的尺寸范围分别为25-30和20-35 nm的范围内，已证明了较高的助催化剂稳定性，较小的D _max（最大平均直径）和混合的形态特征。-TiO ₂纳米复合材料，分别。使用NH ₃气体的吸附-解吸研究表明，与Mn ²⁺浸渍相比，Mn ⁷⁺离子在助催化剂表面产生增强的Lewis酸度。与Mn ²⁺ -TiO ₂和TiO ₂光催化剂相比 ，Mn ⁷⁺ -TiO ₂具有最适合Freundlich吸附等温线的条件（K _f = 23.44μg/ mg），证实了其较高的底物亲和力和光降解效率。Mn ²⁺和Mn ^7+的浸渍显示的光活性是裸TiO _2的2.6和3.7倍这与Mn ^{n +}离子赋予的不同氧化态和表面结构特性有关。