Grafted iron(iii) ions significantly enhance NO2 oxidation rate and selectivity of TiO2 for photocatalytic NOx abatement

摘要

Semiconductor photocatalysis could be an effective means to combat nitrogen oxides (NO _( x ) ) based air pollution through mineralisation of NO _( x ) to nitrate. However, most of the typically TiO _(2) -based catalysts employed show a much higher reactivity towards NO than NO _(2) , leading to an accumulation of this unwanted and toxic intermediate. By grafting the photocatalyst with small amounts (≤0.1 at%) of isolated iron( III ) ions, the reactivity towards NO _(2) is increased by the factor of 9, bringing it up to par with the NO-reactivity and alleviating the problem with intermediate accumulation. Consequently, the observed selectivity of the reaction is dramatically increased from less than 40% to more than 90%. The paper also discusses possible mechanisms for this very beneficial behavior.