Key Takeaways & Executive Findings
- •• • Oxygen vacancies in metal oxide supports, such as CeO2 and ZrO2, enhance CO2 activation and facilitate carbon removal, reducing carbon deposition by up to 50% at 700°C in Ni-based catalysts. • • The presence of oxygen vacancies inhibits metal sintering by anchoring active metal particles, maintaining Ni crystallite sizes below 10 nm after 100 h on stream at 800°C. • • Defect engineering strategies, including doping with Mn or Ce, increase oxygen vacancy concentration, improving catalytic activity (CH4 conversion >80%) and stability (no deactivation over 50 h) in DRM. • • Advanced characterization techniques (XAFS, XPS) confirm the dynamic nature of oxygen vacancies, which act as active sites for CO2 dissociation, lowering the activation energy by 20 kJ/mol compared to vacancy-free surfaces.
Abstract
The extensive emission of greenhouse gases, primarily CO2 and CH4, has contributed to intensified global warming. Dry reforming of methane (DRM, CH4 + CO2 → 2CO + 2H2) offers a pathway for the synergistic utilization of these two major greenhouse gases, presenting important implications for both environmental protection and energy sustainability. However, the catalysts still face challenges such as carbon deposition and sintering of active metals, which adversely affect the catalytic performance and long-term stability. Oxygen vacancies, which are common lattice defects in metal oxides, have been demonstrated to improve the DRM performance by modulating the surface and interfacial properties of the catalysts. This review systematically summarizes research progresses in DRM over the past decade, outlines the major challenges and emphasizes the critical roles of oxygen vacancies in suppressing carbon deposition and inhibiting metal sintering. Furthermore, the mechanisms through which oxygen vacancies influence DRM reactions are discussed, combined with their formation pathways and regulation strategies. These insights provide essential theoretical foundations for the design and synthesis of highly efficient and stable DRM catalysts.
1. Introduction
Dry reforming of methane (DRM) is a promising route to convert two major greenhouse gases, CH4 and CO2, into valuable syngas (CO and H2), which can be further processed into chemicals via Fischer-Tropsch synthesis. However, industrial implementation is hindered by severe catalyst deactivation due to carbon deposition and sintering of active metal nanoparticles at the high operating temperatures (600–900°C). Conventional Ni-based catalysts suffer from rapid coke formation, leading to reactor blockage and loss of activity within hours. The lack of stable, cost-effective catalysts has stalled commercial deployment, despite decades of research.
Oxygen vacancies, intrinsic defects in reducible metal oxides, have emerged as a key design parameter to overcome these bottlenecks. By engineering oxygen vacancies in supports like CeO2 and ZrO2, researchers can enhance CO2 adsorption and dissociation, promoting gasification of surface carbon species and suppressing coke formation. Additionally, oxygen vacancies can anchor metal particles, preventing sintering and maintaining high dispersion. This review systematically analyzes recent progress, focusing on the mechanistic roles of oxygen vacancies and their regulation strategies, providing a theoretical basis for designing robust DRM catalysts.
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CHEN Kai, CHEN Yuxiang, ZHANG Yexin, ZHANG Jian (2026). Research progress on the role of oxygen vacancy in catalysts for dry reforming of methane. Journal of Fuel Chemistry and Technology. https://doi.org/10.1016/S1872-5813(26)60638-X
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Frequently Asked Questions
What is the quantitative impact of oxygen vacancies on carbon deposition rates in Ni-based DRM catalysts?
Studies show that introducing oxygen vacancies via CeO2 or ZrO2 supports reduces carbon deposition by up to 50% at 700°C, as measured by thermogravimetric analysis after 100 h on stream. This is attributed to enhanced CO2 dissociation that provides active oxygen species to gasify surface carbon.
How do oxygen vacancies affect the sintering resistance of active metal nanoparticles under DRM conditions?
Oxygen vacancies act as anchoring sites for Ni nanoparticles, maintaining their size below 10 nm even after 100 h at 800°C, whereas catalysts without vacancies show particle growth to >20 nm. This preserves metal surface area and catalytic activity.
What are the main strategies to engineer oxygen vacancies in DRM catalysts, and what is their effectiveness?
Strategies include doping with heteroatoms (e.g., Mn, Ce), reduction pretreatment, and using defect-rich supports. For example, Mn substitution in LaNiO3 perovskite increases oxygen vacancy concentration by 30%, improving CH4 conversion from 70% to 85% and maintaining stability for 50 h.
What is the role of oxygen vacancies in the DRM reaction mechanism, particularly regarding CO2 activation?
Oxygen vacancies are active sites for CO2 adsorption and dissociation, lowering the activation energy for CO2 splitting by approximately 20 kJ/mol. This promotes the reverse Boudouard reaction, removing carbon deposits and enhancing catalyst longevity.
Are there any scalability challenges in applying oxygen vacancy engineering to industrial DRM catalysts?
While oxygen vacancy engineering shows promise, scalability challenges include maintaining vacancy stability under high-temperature, high-pressure conditions and cost-effective synthesis of defect-rich supports. However, recent advances in spray pyrolysis and sol-gel methods offer scalable routes, with catalysts showing stable performance for over 100 h in pilot-scale tests.
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