*Article* **VOCs Photothermo-Catalytic Removal on MnOx-ZrO<sup>2</sup> Catalysts**

**Roberto Fiorenza \* , Roberta Agata Farina, Enrica Maria Malannata, Francesca Lo Presti and Stefano Andrea Balsamo**

> Dipartimento di Scienze Chimiche, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy; roberta.agata.farina@gmail.com (R.A.F.); enrica.malannata@phd.unict.it (E.M.M.); francesca.lopresti@phd.unict.it (F.L.P.); stefano.balsamo@phd.unict.it (S.A.B.)

**\*** Correspondence: rfiorenza@unict.it; Tel.: +39-0957385012

**Abstract:** Solar photothermo-catalysis is a fascinating multi-catalytic approach for volatile organic compounds (VOCs) removal. In this work, we have explored the performance and the chemicophysical features of non-critical, noble, metal-free MnOx-ZrO<sup>2</sup> mixed oxides. The structural, morphological, and optical characterizations of these materials pointed to as a low amount of ZrO<sup>2</sup> favoured a good interaction and the ionic exchange between the Mn and the Zr ions. This favoured the redox properties of MnOx increasing the mobility of its oxygens that can participate in the VOCs oxidation through a Mars-van Krevelen mechanism. The further application of solar irradiation sped up the oxidation reactions promoting the VOCs total oxidation to CO<sup>2</sup> . The MnOx-5 wt.%ZrO<sup>2</sup> sample showed, in the photothermo-catalytic tests, a toluene T<sup>90</sup> (temperature of 90% of conversion) of 180 ◦C and an ethanol T<sup>90</sup> conversion to CO<sup>2</sup> of 156 ◦C, 36 ◦C, and 205 ◦C lower compared to the thermocatalytic tests, respectively. Finally, the same sample exhibited 84% toluene conversion and the best selectivity to CO<sup>2</sup> in the ethanol removal after 5 h of solar irradiation at room temperature, a photoactivity similar to the most employed TiO<sup>2</sup> -based materials. The as-synthetized mixed oxide is promising for an improved sustainability in both catalyst design and environmental applications.

**Keywords:** VOC; photothermo catalysis; toluene; ethanol; manganese oxide; zirconium oxide
