Noble and non-noble metal catalysts in methane oxidation: a comparative study under various oxidants and low temperatures

Selective oxidation of methane (SOM) offers a sustainable pathway for energy conversion and chemical synthesis. This review critically compares noble metal (Au, Pd, Ru, Rh) and non-noble metal (Fe, Cu, Cr, Zn, Ni) catalysts for methane activation at low-temperature, evaluating their performance under H₂O₂, and O₂ as oxidants in environments, with CO as a promoter. Through a detailed analysis of the structure of typical systems, we have established key design principles involving active site engineering, metal-support interactions, and reactive oxygen species (ROS). Advanced characterization and density functional theory (DFT) studies reveal that metal-oxygen interfaces govern methane activation mechanisms, where dynamic oxygen species, such as O^*, OH^*, and OOH^*, dictate reaction pathways. Catalyst dimensionality, such as single-atom vs. clusters, and electronic modifications are shown to critically influence C-H bond cleavage energetics and methanol desorption. While noble metals excel in oxygen activation, modified non-noble catalysts achieve comparable efficacy by optimizing their coordination environments. This review summarizes recent advances in the SOM under mild conditions, providing a systematic qualitative and quantitative kinetic comparison of noble metal and non-noble metal catalysts across various oxidant systems. It offers valuable insights into reaction pathways and mechanisms in different catalytic environments, contributing to a deeper understanding of methane activation and functionalization. It is anticipated that this review will provide a useful guide to chemists and material scientists attempting to design better metal catalysts for the SOM.