This study investigates the role of metastable nickel–oxygen species in modulating rate oscillations during dry reforming of methane (DRM) on a nickel catalyst. Using environmental scanning electron microscopy (ESEM), near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), on-line product detection, and computer vision, the researchers observed how different metastable oxygen species—atomic surface oxygen, subsurface oxygen, and bulk NiOx—interconvert during DRM, leading to oscillations in reaction rates. These oscillations are attributed to the dynamic interplay between these oxygen species, which influence the activation of methane and the oxygen content of the catalyst. The study highlights the importance of metastability and operando analytics in understanding catalytic processes. It shows that the catalyst surface undergoes continuous transformations, with oxygen species playing a critical role in regulating the reaction. The research reveals that the oscillations arise from the sequential transformation of these metastable oxygen species, which have distinct catalytic properties. The findings suggest that the dynamic nature of the catalyst surface, with fluctuating regions of activity, is key to the observed oscillatory behavior. The study also demonstrates that the presence of different oxygen forms—such as surface, subsurface, and bulk oxygen—can significantly affect the catalytic performance. The oscillations are linked to the redox transitions of the catalyst, with the formation and consumption of oxides playing a central role. The results indicate that the catalyst's activity is closely tied to the balance between these oxygen species, with their interconversion driving the oscillations. The research provides insights into the mechanisms underlying catalytic activity and the importance of metastable states in heterogeneous catalysis. It underscores the need for advanced analytical techniques to study these dynamic processes and highlights the potential for designing more efficient catalytic systems by understanding and controlling the metastable states of oxygen species. The findings contribute to the broader understanding of catalytic science and have implications for the development of more effective catalysts for industrial applications.This study investigates the role of metastable nickel–oxygen species in modulating rate oscillations during dry reforming of methane (DRM) on a nickel catalyst. Using environmental scanning electron microscopy (ESEM), near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), on-line product detection, and computer vision, the researchers observed how different metastable oxygen species—atomic surface oxygen, subsurface oxygen, and bulk NiOx—interconvert during DRM, leading to oscillations in reaction rates. These oscillations are attributed to the dynamic interplay between these oxygen species, which influence the activation of methane and the oxygen content of the catalyst. The study highlights the importance of metastability and operando analytics in understanding catalytic processes. It shows that the catalyst surface undergoes continuous transformations, with oxygen species playing a critical role in regulating the reaction. The research reveals that the oscillations arise from the sequential transformation of these metastable oxygen species, which have distinct catalytic properties. The findings suggest that the dynamic nature of the catalyst surface, with fluctuating regions of activity, is key to the observed oscillatory behavior. The study also demonstrates that the presence of different oxygen forms—such as surface, subsurface, and bulk oxygen—can significantly affect the catalytic performance. The oscillations are linked to the redox transitions of the catalyst, with the formation and consumption of oxides playing a central role. The results indicate that the catalyst's activity is closely tied to the balance between these oxygen species, with their interconversion driving the oscillations. The research provides insights into the mechanisms underlying catalytic activity and the importance of metastable states in heterogeneous catalysis. It underscores the need for advanced analytical techniques to study these dynamic processes and highlights the potential for designing more efficient catalytic systems by understanding and controlling the metastable states of oxygen species. The findings contribute to the broader understanding of catalytic science and have implications for the development of more effective catalysts for industrial applications.