Solar photothermo-catalytic CO2 conversion into methane: Effect of phyllosilicates on the performance of Ni-Zn-Al layered double hydroxide-derived catalysts

The development of efficient catalysts for CO₂ utilization is a key challenge for industrial sustainability. This study explores the photothermo-catalytic methanation of CO₂ using Ni-Zn-Al Layered Double Hydroxide-derived (LDHd) catalysts modified with phyllosilicates (Montmorillonite K30 and Halloysite). LDH precursors were synthesized by co-precipitation and hydrothermal treatment, then calcined and reduced leading to the formation of mixed oxides and metallic Ni and Zn nanoparticles. Catalytic performances were evaluated at 1 atm and 350 °C. The Ni-Zn-Al LDHd catalyst achieved high CO₂ conversion (86 %) and CH₄ selectivity (>99 %) under photothermo-catalytic conditions, outperforming commercial Ni systems. Incorporation of halloysite, thermally treated at 200 °C, further increased CO₂ conversion to 92 % with the same high CH₄ selectivity. This improved performance is attributed to enhanced surface area, optical absorption and moderate–strong basic sites from LDHd–Halloysite interaction. In contrast, Montmorillonite modification, despite cetyltrimethylammonium bromide (CTAB) intercalation, resulted in lower activity and selectivity, due to weaker basicity and ineffective LDHd interaction. The Ni-Zn-Al LDHd/halloysite catalyst exhibited excellent stability during 20 h of continuous photothermo-catalytic test at 350 °C. These results demonstrate the potential of phyllosilicate-modified LDH-derived catalysts, with low metals content, for efficient CO₂ methanation under solar irradiation.