Through our previous studies it was established that non- precious Fe₂O₃ based catalyst has the potential to replace Pt based catalyst for high temperature sulfuric acid decomposition, the energy conversion step in iodine- sulfur or hybrid-sulfur thermochemical cycles for water splitting (Banerjee et al. [11] and [25]). However, issues like agglomeration and grain growth during prolonged operation still remain to be fully resolved. With an aim to develop low cost, abundant transition metal oxide catalyst with high activity and stability, Fe₂O₃ nanoparticles immobilized on SiO₂ support is explored, anticipating that the Fe₂O₃-SiO₂ interactions may prevent self agglomeration of Fe₂O₃ nanoparticles. Several catalysts with varying Fe₂O₃ content ranging from 5 to 20 wt% were synthesized, characterized and their catalytic activity evaluated. Structural investigations by XRD and Mössbauer spectroscopy revealed that the 1000 °C calcined samples contained ε-Fe₂O₃ as the major phase in addition to minor α and γ-Fe₂O₃ phases. ε-Fe₂O₃ were found to be dispersed as nanorods with typical width of 5 nm from HRTEM images. Analysis of surface features by N₂-BET surface area, pore size distribution, pore volume and XPS indicated that the majority of Fe₂O₃ was encapsulated within the mesoporous structure of SiO₂ upto 15 wt.%, beyond which Fe₂O₃ was deposited outside the porous network in an enhanced quantity. The surface area of Fe₂O₃(15 wt.%)/SiO₂ was found to be 99.6 m²/g. Presence of Fe-O-Si linkages was confirmed by XPS, and supported by successive TPR/TPO studies. The extent of reducibility measured via TPR increased with increasing loading and was found to be maximum for the 15 wt.% dispersed samples. The catalytic activity was found to increase with an increase in loading of active Fe₂O₃ content upto a SO₂ yield of ∼ 92% at 900 °C at a WHSV of 27 g acid g⁻¹ h⁻¹, for 15 wt.% and then decreased. Further evaluation of the 15 wt.% sample revealed the durability (100 h) and practical applicability of the composition. The surface morphology, structure and composition underwent modifications during the 100 h operation in order to adapt to the reaction environment (high temperature, steam, oxides of sulfur) and the Fe₂O₃ (15 wt.%)/SiO₂ catalyst exhibited iron sulfate formation and significant surface reorganization. The high catalytic activity can be ascribed to nanoparticulate nature of Fe₂O₃ and stability due to its anchored structure on SiO₂. These findings would inspire the design of active and stable catalyst for high temperature catalytic reactions.

通过我们先前的研究，确定了非贵重的Fe ₂ O ₃基催化剂有可能替代Pt基催化剂用于高温硫酸分解，碘-硫或杂化-硫热化学循环中的能量转化步骤（用于水分解）（ Banerjee等人[11]和[25]）。但是，长时间运行过程中的结块和晶粒长大等问题仍然有待完全解决。为了开发低成本，高活性和高稳定性的丰富过渡金属氧化物催化剂，研究了固定在SiO ₂载体上的Fe ₂ O ₃纳米颗粒，并预期Fe ₂ O ₃ -SiO₂相互作用可能会阻止Fe ₂ O ₃纳米粒子的自团聚。合成了几种Fe ₂ O ₃含量在5至20 wt％范围内的催化剂，进行了表征，并评估了其催化活性。通过XRD和穆斯堡尔结构调查光谱表明，1000℃下焙烧样品含有ε -铁₂ ö ₃为除了轻微的α和γ-Fe由于主要阶段₂ ö _3个相。ε -铁₂ ö ₃被发现被分散为具有从HRTEM图像5纳米的典型宽度的纳米棒。用N ₂分析表面特征-BET表面积，孔尺寸分布，孔体积和XPS表明，大部分Fe ₂ O ₃包封在SiO ₂的介孔结构中，含量高达15 wt。％，超过此范围，Fe ₂ O ₃沉积在SiO ₂的多孔网络外部。数量增加。发现Fe ₂ O ₃（15重量％）/ SiO ₂的表面积为99.6m ^2。/G。XPS证实了Fe-O-Si键的存在，并得到连续TPR / TPO研究的支持。通过TPR测得的还原性程度随上样量的增加而增加，并且发现对于15重量％的分散样品是最大的。发现在900 g的WHSV为27 g酸g ^-1  h ^-1时，催化活性随活性Fe ₂ O ₃含量的增加而增加，直至SO ₂收率达到〜92 ％。含量为15 wt。％，然后下降。对15重量％的样品的进一步评估显示了该组合物的耐久性（100小时）和实际适用性。为了适应反应环境（高温，蒸汽，硫的氧化物），在100小时的操作过程中对表面形态，结构和组成进行了修饰，并且Fe ₂ O ₃（15 wt。％）/ SiO ₂催化剂显示出铁硫酸盐的形成和明显的表面重组。Fe ₂ O _3的纳米颗粒性质和由于其在SiO ₂上的锚固结构而具有较高的催化活性。。这些发现将启发用于高温催化反应的活性和稳定催化剂的设计。