Insight into the effect of manganese substitution on mesoporous hollow spinel cobalt oxides for catalytic oxidation of toluene

Peng Liu; Yuxi Liao; Jingjing Li; Longwen Chen; Mingli Fu; Puqiu Wu; Runliang Zhu; Xiaoliang Liang; Tianli Wu; Daiqi Ye

doi:10.1016/j.jcis.2021.03.093

Insight into the effect of manganese substitution on mesoporous hollow spinel cobalt oxides for catalytic oxidation of toluene

J Colloid Interface Sci. 2021 Jul 15:594:713-726. doi: 10.1016/j.jcis.2021.03.093. Epub 2021 Mar 19.

Authors

Peng Liu¹, Yuxi Liao¹, Jingjing Li¹, Longwen Chen¹, Mingli Fu², Puqiu Wu³, Runliang Zhu³, Xiaoliang Liang³, Tianli Wu⁴, Daiqi Ye⁵

Affiliations

¹ School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China.
² School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China; National Engineering Laboratory for VOCs Pollution Control Technology and Equipment, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China; Guangdong Provincial Engineering and Technology Research Centre for Environmental Risk Prevention and Emergency Disposal, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China.
³ Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China.
⁴ Henan Key Laboratory of Photovoltaic Materials, Henan University, Kaifeng 475004, PR China.
⁵ School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China; National Engineering Laboratory for VOCs Pollution Control Technology and Equipment, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China; Guangdong Provincial Engineering and Technology Research Centre for Environmental Risk Prevention and Emergency Disposal, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China. Electronic address: cedqye@scut.edu.cn.

PMID: 33794399
DOI: 10.1016/j.jcis.2021.03.093

Abstract

The cobalt oxides and manganese oxides have high-activity potential for catalytic oxidation of volatile organic compounds (VOCs), while the mesoporous hollow morphology is crucial to the mass transfer of reactant and product. Therefore, it is worth investigating the effect of manganese substitution in mesoporous hollow cobalt oxides on catalytic oxidation. Herein, a partially disordered spinel structure is formed by the Mn substitution in Co₃O₄ and the mesoporous hollow microsphere is improved in morphology homogeneity with the decrease of Co/Mn ratio in the range of 1.8-28.8. The 5Co1Mn (Mn-substituted Co₃O₄ with Co/Mn at 5.4) exhibits outstanding catalytic activity for toluene oxidation with 50% CO₂ generation at 237 °C, which is 21 °C lower than Co₃O₄. Moreover, the 5Co1Mn displays satisfactory stability in reusability, lifetime, and water resistance. The small defective crystallite, mesoporous hollow morphology, and high specific surface area endow Mn-substituted Co₃O₄ with more surface chemical adsorbed oxygen, enhancing the catalytic oxidation of toluene. Theoretical calculation on (311) plane of Co₃O₄ reveals that Mn²⁺ or Mn³⁺ substitution increases the formation energy of oxygen vacancy and makes it difficult to adsorb gaseous oxygen on the defective surface. The interaction between Co and Mn impedes the improvement of toluene oxidation because the mobility of lattice oxygen, the surface distribution of Co³⁺, and the ratio of surface adsorbed oxygen to surface lattice oxygen are hindered by Mn substitution. The chemical adsorbed oxygen is more active than lattice oxygen in the oxidation of adsorbed intermediates (phenolate, benzoate species, etc.). The Langmuir-Hinshelwood mechanism dominates in the catalytic oxidation at 200-250 °C, while the catalytic oxidation follows both the Langmuir-Hinshelwood mechanism and Mars-van Krevelen mechanism above 250 °C. This work provides some enlightenment for exploring the role of surface oxygen species in VOCs oxidation and uncovering the interaction in binary spinel oxides.

Keywords: Catalytic mechanism; Catalytic oxidation; In situ DRIFTS; Mesoporous hollow Co(3)O(4); Mn substitution.