The Development of Ni-Al Aerogel-Based Catalysts via Supercritical CO2 Drying for Photocatalytic CO2 Methanation

The conversion of CO2 into CH4 through the Sabatier reaction is one of the key processes that can reduce CO2 emissions into the atmosphere. This work aims to develop Ni-Al aerogel-based thermo-photocatalysts with large specific surface areas prepared using a sol–gel method and subsequent supercritical drying in CO2. Different Al/Ni molar ratios were selected for the development of the catalysts, characterized using ICP-OES, N2 adsorption–desorption isotherms, XRD, H2-TPR, TEM, UV-Vis DRS, and XPS techniques. Thermo-photocatalytic activity tests were performed in a photoreactor with two different light sources (λ = 365 nm, λ = 470 nm) at a temperature range from 300 °C to 450 °C and a pressure of 10 bar. The catalyst with the highest Ni loading (AG 1/3) produced the best catalytic results, reaching CO2 conversion and CH4 selectivity levels of 82% and 100%, respectively, under visible light at 450 °C. In contrast, the catalysts with the lowest nickel loading produced the lowest results, most likely due to their low amounts of active Ni. These results suggest that supercritical drying is an efficient method for developing active thermo-photocatalysts with high Ni dispersion, suitable for Sabatier reactions under mild reaction conditions.