*Article* **Hydrogen Photo-Production from Glycerol Using Nickel-Doped TiO2 Catalysts: E**ff**ect of Catalyst Pre-Treatment**

#### **Jesús Hidalgo-Carrillo \*, Juan Martín-Gómez, Julia Morales, Juan Carlos Espejo, Francisco José Urbano and Alberto Marinas**

Departamento de Química Orgánica, Instituto Universitario de Investigación en Química Finay Nanoquímica (IUNAN), Universidad de Córdoba, E-14071 Córdoba, Spain

**\*** Correspondence: jesus.hidalgo@uco.es

Received: 20 July 2019; Accepted: 30 August 2019; Published: 30 August 2019

**Abstract:** In the present piece of research, hydrogen production via the photo-reforming of glycerol (a byproduct from biodiesel generation) is studied. Catalysts consisted of titania modified by Ni (0.5% by weight) obtained through deposition–precipitation or impregnation synthetic methods (labelled as Ni-0.5-DP and Ni-0.5-IMP, respectively). Reactions were performed both under UV and solar irradiation. Activity significantly improved in the presence of Ni, especially under solar irradiation. Moreover, pre-reduced solids exhibited higher catalytic activities than untreated solids, despite the "in-situ" reduction of nickel species and the elimination of surface chlorides under reaction conditions (as evidenced by XPS). It is possible that the catalyst pretreatment at 400 ◦C under hydrogen resulted in some strong metal–support interactions. In summary, the highest hydrogen production value (ca. 2600 micromole H2·g<sup>−</sup>1) was achieved with pre-reduced Ni-0.5-DP solid using UV light for an irradiation time of 6 h. This value represents a 15.7-fold increase as compared to Evonik P25.

**Keywords:** hydrogen production; photo-reforming; glycerol; Ni/TiO2
