Influence of entropy on catalytic performance of high-entropy oxides (NiMgZnCuCoOx) in peroxymonosulfate-mediated acetaminophen degradation.

Developing a high-performance activator is crucial for the practical application of peroxymonosulfate-based advanced oxidation processes (PMS-AOPs). High-entropy oxides (HEOs) have attracted increasing attention due to their stable crystal structure, flexible composition and unique functionality. However, research into the mechanisms by which HEOs function as PMS activators for degrading organic pollutants remains insufficient, and the relationship between entropy and the catalytic performance of HEOs has yet to be clarified. In this study, we synthesized NiMgZnCuCoOx with different levels of entropy as PMS activators for acetaminophen (APAP) degradation, and observed a significant effect for entropy on the catalytic performance. Sulfate radicals (SO4•‒) were identified as the primary reactive oxygen species (ROS), while hydroxyl radicals (•OH) and singlet oxygen (1O2) act as secondary ROS during APAP degradation. Both the Co2+ contents and the oxygen vacancy concentration in NiMgZnCuCoOx are found to increase with the entropy. An increase in the Co2+ sites leads to more activation sites for PMS activation, while excessive oxygen vacancies consume PMS, producing weak oxidation species, and affect the electron-donating ability of Co2+. Consequently, the NiMgZnCuCoOx with middle level of entropy exhibits the optimal performance with APAP degradation rate and mineralization rate reaching 100% and 74.22%, respectively. Furthermore, the degradation intermediates and their toxicities were assessed through liquid chromatography-mass spectrometry and quantitative structure-activity relationship analysis. This work is expected to provide critical insight into the impact of the HEOs entropy on the PMS activation and guide the rational design of highly efficient peroxymonosulfate activators for environmental applications.

Modulating Metal-Nitrogen Coupling in Anti-Perovskite Nitride via Cation Doping for Efficient Reduction of Nitrate to Ammonia.

The complexes of metal center and nitrogen ligands are the most representative systems for catalyzing hydrogenation reactions in small molecule conversion. Developing heterogeneous catalysts with similar active metal-nitrogen functional centers, nevertheless, still remains challenging. In this work, we demonstrate that the metal-nitrogen coupling in anti-perovskite Co4 N can be effective modulated by Cu doping to form Co3 CuN, leading to strongly promoted hydrogenation process during electrochemical reduction of nitrate (NO3 - RR) to ammonia. The combination of advanced spectroscopic techniques and density functional theory calculations reveal that Cu dopants strengthen the Co-N bond and upshifted the metal d-band towards the Fermi level, promoting the adsorption of NO3 - and *H and facilitating the transition from *NO2 /*NO to *NO2 H/*NOH. Consequently, the Co3 CuN delivers noticeably better NO3 - RR activity than the pristine Co4 N, with optimal Faradaic efficiency of 97 % and ammonia yield of 455.3 mmol h-1 cm-2 at -0.3 V vs. RHE. This work provides an effective strategy for developing high-performance heterogeneous catalyst for electrochemical synthesis.