Photocatalytic O₂ activation to generate reactive oxygen species is crucially important for purifying organic pollutants, yet remains a challenge due to poor adsorption of O₂ and low efficiency of electron transfer. Herein, we demonstrate that ultrafine MoO_x clusters anchored on graphitic carbon nitride (g-C₃N₄) with dual nitrogen/oxygen defects promote the photocatalytic activation of O₂ to generate ·O₂⁻ for the degradation of tetracycline hydrochloride (TCH). A range of characterization techniques and density functional theory (DFT) calculations reveal that the introduction of the nitrogen/oxygen dual defects and MoO_x clusters enhances the O₂ adsorption energy from −2.77 to −2.94 eV. We find that MoO_x clusters with oxygen vacancies (Ov) and surface Ov-mediated Mo^δ+ (3 ≥ δ ≥ 2) possess unpaired localized electrons, which act as electron capture centers to transfer electrons to the MoO_x clusters. These electrons can then transfer to the surface adsorbed O₂, thus promoting the photocatalytic conversion of O₂ to ·O₂⁻ and, simultaneously, realizing the efficient separation of photogenerated electron–hole pairs. Our fully-optimized MoO_x/g-C₃N₄ catalyst with dual nitrogen/oxygen defects manifests outstanding photoactivities, achieving 79% degradation efficiency toward TCH within 120 min under visible light irradiation, representing nearly 7 times higher activity than pristine g-C₃N₄. Finally, based on the results of liquid chromatograph mass spectrometry and DFT calculations, the possible photocatalytic degradation pathways of TCH were proposed.

The Haber–Bosch process is the dominant approach for NH₃ production today, but the process has to be maintained at energy-intensive high temperatures and pressures. Li-mediated electrocatalytic dinitrogen reduction reaction (eN₂RR) could instead enable sustainable and green NH₃ production at ambient conditions. Lithium mediators realize the synthesis of NH₃ via the formation of Li₃N, and thus lower the energy required for the direct cleavage of N₂. There has now been a surge of interest in devising approaches to optimize the NH₃ yield rate and faradaic efficiency of the eN₂RR process by employing different catalysts as well as electrolytes. This review discusses the recent advances in the field of the Li-mediated eN₂RR along with the latest insights into the proposed catalytic mechanisms. Moreover, it also highlights the state-of-the-art reported electrocatalysts and electrolytes that have revolutionized the field of the Li-mediated eN₂RR. In addition to the above, our review provides a critical overview of certain limitations and a future prospectus that will provide a way forward to explore this area.