Oxygen Vacancy Modulation via Confinement: Enhanced Dry Reforming Activity and Stability of Nickel-Cerium Catalysts Encapsulated in Titanium Silicalite-1 Zeolite
Abstract
The advancement of anti-coking catalysts for dry reforming of methane (DRM) is essential for mitigating greenhouse gas emissions and promoting sustainable syngas production. Herein, a series of nickel-cerium (CeNi@TS-1) catalysts for the DRM was synthesized via impregnation-recrystallization. Among these, 12CeNi@TS-1 exhibited markedly superior catalytic activity achieving conversion rates of 81.2% for methane (CH4) and 92.3% for carbon dioxide (CO2), with specific activities of 4.83 mmolCH4⋅gNi-1⋅s−1 and 5.48 mmolCO2⋅gNi-1⋅s−1. For 12CeNi@TS-1 following 50 h of operation, minimal activity loss of less than 0.5% was observed for both CH4 and CO2, indicating good stability. Physical and morphological analyses revealed that appropriate CeO2 content effectively reduced and dispersed the nickel (Ni) nanoparticles (NPs) while maintaining the MFI structure, also enhancing the interactions between the Ni NPs, TS-1, and ceria (CeO2). This modification fostered a rich environment of oxygen vacancies (OVs). Hence, the prevalence of Ni NPs in stronger electron-deficient states was increased, along with the number of basic sites conducive to synergistic activation of CH4 and CO2. In-Situ DRIFTS spectroscopy analysis indicated that CeO2 introduction in 12CeNi@TS-1 enhanced the CH4 and CO2 activation, while suppressing excessive CH4 cracking and carbon accumulation by OVs. This work provides significant insights into the effective utilization of greenhouse gases for sustainable energy conversion.