Nickel-Decorated Carbocatalysts for the UV-Driven Photodegradation of Rhodamine B

Nickel-decorated carbocatalysts were synthesized by the evaporation-induced self-assembly (EISA) method. The influence of the metal content and pyrolysis temperature upon the photoactivity was assessed through rhodamine B degradation under UV irradiation. The characterization revealed a mesoporous framework with a granular morphology composed of amorphous carbon, where the pyrolysis temperature influenced the metal dispersion on the carbon surface. The primary metallic phases consisted of elemental nickel crystallites and nickel carbide phases. The kinetic parameters for adsorption and dye photodegradation under UV irradiation were determined and compared to TiO2-P25. Correlations were found between the adsorption parameters, photocatalytic activity, and nickel content, the pyrolysis method (one-step vs. two-step pyrolysis), and the pyrolysis temperature. The sample with a 1:1:0.25 tannin/Pluronic®F-127/Ni weight ratio pyrolyzed at 700 °C exhibited the highest photoactivity, achieving rhodamine B degradation rates up to 68 and 2.5 times greater than photolysis and TiO2-P25. In terms of the normalized weight of the catalysts, it can be concluded that the present Ni-based catalysts are up to two orders of magnitude more photoactive than TiO2-P25 under UV irradiation, opening a door for indoor UV-driven photoreactors. These findings demonstrate that the EISA method is an effective, low-cost, and ecofriendly approach for synthesizing Ni-decorated carbocatalysts.