Synergistic Tuning of Oxygen Vacancies, Basic Sites, and Metal−Support Interaction in NiAlCeLa LDH-Derived Catalyst for Low-Temperature CO2 Methanation

Abstract

Developing Ni-based catalysts for low-temperature CO<inf>2</inf> methanation remains challenging due to the kinetic limitation. Layered double hydroxides (LDHs) have emerged as versatile catalyst precursors enabling structural tunability through cation incorporation. Here, we report a stepwise catalyst design strategy implemented at the LDH stage, in which Ce and La are simultaneously incorporated into NiAl-LDH to engineer structural defects and catalytic functionality. A series of NiAl-LDH, NiAlCe-LDH, and NiAlCeLa-LDH materials was synthesized via a one-pot hydrothermal method with designated metal ratios (Ni/Al= 1−5, Ce/Al = 0.2−1.0, and La/Ce = 0.025−1.0). Systematic characterization reveals that oxygen vacancies (O<inf>V</inf>), weak and medium basic sites (WBS/MBS), and metal−support interaction (MSI) govern the catalytic activity of the catalysts. Incorporation of Ce into Ni<inf>2</inf>Al-LDH generates abundant O<inf>V</inf>, while subsequent La introduction into Ni<inf>2</inf>AlCe<inf>0.4</inf>La<inf>0.05</inf>-LDH provides additional structural and electronic benefits. Upon calcination, insertion of La into the ceria lattice of Ni<inf>2</inf>AlCe<inf>0.4</inf>La<inf>0.05</inf> further amplifies O<inf>V</inf> formation, enriches WBS/MBS, and enhances NiO reducibility and interfacial Ni electron density. Owing to these synergistic effects, Ni<inf>2</inf>AlCe<inf>0.4</inf>La<inf>0.05</inf> provides 85% CO<inf>2</inf> conversion, a CH<inf>4</inf> production rate of 69.5 mmol g⁻¹ h⁻¹, and a TOF of 0.35 s⁻¹ at 180 °C. In situ DRIFTS analysis reveals that OH groups and O<inf>V</inf> in Ni<inf>2</inf>AlCe<inf>0.4</inf>La<inf>0.05</inf> facilitate CO<inf>2</inf> activation into HCO<inf>3</inf> and b-CO<inf>3</inf> species, which are easily hydrogenated to CH<inf>4</inf> via the formate pathway. This work establishes a rational catalyst design strategy to integrate O<inf>V</inf> formation, surface basicity modulation, and MSI tuning for low-temperature CO<inf>2</inf> methanation.