2.1.1. Deposition–precipitation Method

The deposition-precipiation method was used for incorporation of nickel on P25 Evonik with a nominal weight of 0.5%. The incorporation of Nickel was carried out in a "Contalab" system (Switzerland) enabling careful control of all the variables, i.e., pH, temperature, stirrer speed, reactant feed flow, etc. Firstly in 150 mL distilled water were dispersed 5 g of P25 Evonik using ultrasound. The deposition of the nickel was carried out at 60 ◦C and a pH of 6.8, keeping it constant with an 0.2 M aqueous solution of K2CO3 (Sigma Aldrich). Next, an aqueous solution of 2 <sup>g</sup>·L−<sup>1</sup> of nickel (using NiCl2 (Sigma Aldrich)) was added dropwise and the mixture was maintained for 1 h at 60 ◦C. Then the solid obtained was filtered and washed with distilled water. Then, the solid was dried at 110 ◦C overnight. Finally, the solids were calcined at 400 ◦C for 6 h (using a ramp rate of 10 ◦C·min−1).
