Interfacial coupling between Ni(OH)₂ nanoparticles and oxygen deficient TiO2 drives high yield CO2 methanation

This study highlights the critical role of interfacial coupling between Ni(OH)2 nanoparticles and oxygen-deficient TiO2 in governing CO₂ methanation performance. Ni(OH)₂ nanoparticles with controlled loadings (1, 5, and 10 wt%) were grown on TiO2 support to systematically study the effect of metal-support interaction on catalytic activity. The results of Raman and X-ray photoelectron spectroscopy confirmed the generation of progressively increasing oxygen vacancies in TiO2 support with increasing Ni loading via substitution of Ti4+ by Ni2+ in TiO2 lattice. In addition, HRTEM images revealed the formation of well-defined Ni(OH)2 -TiO2 interfacial regions in 5 wt% Ni loading case (denoted as Ni-5@TiO2), promoting efficient electron transfer from TiO₂ to Ni sites. This strong interfacial electronic coupling enhances CO2 activation at oxygen-vacant TiO₂ sites and H₂ dissociation at nearby Ni sites, creating a highly active dual-site environment for CH₄ formation. The optimized Ni-5@TiO₂ catalyst achieved a CH₄ yield of 3814 µmol g⁻¹ at 573 K, outperforming the 1 wt% (1496 µmol g⁻¹) and 10 wt% (2960 µmol g⁻¹) catalysts by 61% and 22%, respectively. Structural analysis confirmed that excessive agglomeration at low Ni loading and Ni(OH)₂ diffusion into the TiO₂ lattice at high loading hinder interface formation. These results establish defect-mediated interfacial engineering as a key strategy for developing efficient, durable, and low-cost catalysts for CO₂ hydrogenation.