Iron doped effects on active sites formation over activated carbon supported Mn-Ce oxide catalysts for low-temperature SCR of NO

To clarify the Fe doped effects over activated carbon (AC) supported Mn-Ce oxide catalysts and study the influence of Fe addition on the AC, several Mn/Ce/Fe mixed oxide catalysts prepared via an impregnation method supported on AC were investigated for low-temperature selective catalytic reduction (SCR) of NO with NH₃. The Mn-Ce-Fe/AC catalyst with 5% (mass ratio) loading exhibited the highest catalytic activity and yielded above 90% NO conversion at 125 °C with a space velocity of 12,000 h⁻¹. The Fe addition could obviously reduce the destruction of AC surface area. Also, the metal ions could insert into graphite crystallite structures of AC, splitting it into smaller graphene-like sheets. After doping with Fe species, the relative ratios of Mn⁴⁺/Mnⁿ⁺, Ce³⁺/Ceⁿ⁺ and the surface adsorbed oxygen greatly enhanced in Mn-Ce-Fe/AC catalyst. Additionally, both weak acid and medium acid amount increased significantly after the Fe species introduced in Mn-Ce/AC, which could be attributed to the more exposed active sites of acid due to Fe species or its influence on Mn/Ce species. Relying on the obtained results, a L-H mechanism was proposed, owing to the Fe doping, the average valence state of Mn ions and surface adsorbed oxygen both increased on the Mn-Ce-Fe/AC catalyst, specially accompanying with the surface acid sites promotion, therefore remarkably promoting the denitration efficiency due to all the cumulative effect.