Photocatalytic reduction of NO with ethanol on Au/TiO2

•Photolysis of NO + C2H5OH, NO + CH3CHO, and Au-promoted TiO2.•Formation of NCO in the photoreduction of NO.•Photolysis in visible light.

The effect of illumination on the surface interaction and the reaction between NO + C2H5OH was investigated on Au/TiO2 catalyst. By means of Fourier transform infrared spectroscopy, the formation of absorption bands at ∼2180 and ∼2210 cm−1 was observed. The first was attributed to the NCO species locating on Au particles, and the second one to NCO residing on the TiO2 support. While the thermal reaction between NO and C2H5OH on Au/TiO2 catalyst occurred with measurable rate only at and above 473–523 K, illumination of the system induced the reaction even at room temperature. A fraction of NO was converted into N2O, another one to N2. At the same time, the photo-induced decomposition of C2H5OH also occurred yielding CH3CHO, H2, CO, and CH4. Interestingly, the presence of NO significantly slowed down the rate of the decomposition of C2H5OH. Separate studies revealed that all the products formed in the decomposition of C2H5OH reacted with NO. A mechanism for the photocatalytic reduction of NO with C2H5OH is proposed taking into account the effects of the products of C2H5OH photolysis. Incorporation of N into TiO2, which significantly lowered its band gap, appreciably enhanced the reduction of NO, which occurred even in visible light.

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