Unveiling the active phase of catalytic materials under reaction conditions is important for the construction of efficient electrocatalysts for selective nitrate reduction to ammonia. The origin of the prominent activity enhancement for CuO (Faradaic efficiency: 95.8 %, Selectivity: 81.2 %) toward selective nitrate electroreduction to ammonia was probed. 15N isotope labeling experiments showed that ammonia originated from nitrate reduction. 1H NMR spectroscopy and colorimetric methods were performed to quantify ammonia. In situ Raman and ex situ experiments revealed that CuO was electrochemically converted into Cu/Cu2O, which serves as an active phase. The combined results of online differential electrochemical mass spectrometry (DEMS) and DFT calculations demonstrated that the electron transfer from Cu2O to Cu at the interface could facilitate the formation of *NOH intermediate and suppress the hydrogen evolution reaction, leading to high selectivity and Faradaic efficiency.

Electrocatalytic nitrate reduction into recyclable ammonium under benign conditions is significant. However, the development of such a process has been retarded by the lack of efficient electrocatalysts for highly selective synthesis of ammonia from nitrate electroreduction. In this work, TiO 2 nanotubes with rich oxygen vacancies (TiO 2-x ) are reported to exhibit high Faradaic efficiency (85.0%) and selectivity (87.1%) toward the ammonium synthesis from nitrate electroreduction. 15 N isotope labeling experiments prove that ammonium originates from nitrate reduction. Both the 1 H nuclear magnetic resonance (NMR) spectra and colorimetric methods are performed to quantify ammonia. Online differential electrochemical mass spectrometry (DEMS) and density functional theory calculations reveal the function of oxygen vacancy in nitrate electroreduction, that is, the oxygen atom in nitrate fills in oxygen vacancies of TiO 2-x to weaken the N−O bonding and restrain the formation of byproducts, resulting in high Faradaic efficiency and ammonium selectivity. This strategy may open a paradigm for the development of rationally designed nanostructures as the electrocatalysts for selective nitrate electroreduction to ammonium.

Commercial nitric acid (HNO3) and ammonia (NH3) are mostly produced through the Ostwald process and the Haber-Bosch process, respectively. However, high energy demand and enormous greenhouse gas accompy these processes. The development of economical and green ways to synthesize HNO3 and NH3 is highly desirable for solving the global energy and environmental crisis. Here, we present two energy-efficient and environmentally friendly strategies to synthesize HNO3 and NH3 at distributed sources, including the electrocatalytic oxidation of N2 in air to HNO3 and the electrocatalytic reduction of residual ${\rm NO_{3}^{-}}$ contamination in water to NH3. The isotope-labeling studies combined with theoretical calculation reveal the reaction path of the two proposed strategies, confirming the origin of the electrochemical products. Importantly, the electrooxidation-generated ${\rm NO_{3}^{-}}$ ions may also serve as reactants for the electroreduction synthesis of NH3 in the future. Our work may open avenues for energy-efficient and green production of HNO3 and NH3 at distributed sources.

Unveiling the active phase of catalytic materials under reaction conditions is important for the construction of efficient electrocatalysts for selective nitrate reduction to ammonia. The origin of the prominent activity enhancement for CuO (Faradaic efficiency: 95.8 %, Selectivity: 81.2 %) toward selective nitrate electroreduction to ammonia was probed. 15N isotope labeling experiments showed that ammonia originated from nitrate reduction. 1H NMR spectroscopy and colorimetric methods were performed to quantify ammonia. In situ Raman and ex situ experiments revealed that CuO was electrochemically converted into Cu/Cu2O, which serves as an active phase. The combined results of online differential electrochemical mass spectrometry (DEMS) and DFT calculations demonstrated that the electron transfer from Cu2O to Cu at the interface could facilitate the formation of *NOH intermediate and suppress the hydrogen evolution reaction, leading to high selectivity and Faradaic efficiency.

Two different concentrations of D-galactose (D-gal) induced organism and skin aging in Kunming mice were used to examine comprehensively the antioxidant and antiaging activities of ethyl acetate extraction (EAE) from Idesia polycarpa defatted fruit residue for the first time. The oxygen radical absorbance capacity (ORAC) of EAE was 13.09 ± 0.11 μmol Trolox equivalents (TE)/mg, which showed EAE had great in vitro free radical scavenging and antioxidant activity. Biochemical indexes and morphological analysis of all tested tissues showed that EAE could effectively improve the total antioxidant capacity (T-AOC) of the antioxidant defense system of the aging mice, enhance the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) of tissues and serum, increase glutathione (GSH) content and decrease the malondialdehyde (MDA) content, and maintain the skin collagen, elastin, and moisture content. Meanwhile, EAE could effectively attenuate the morphological damage in brain, liver, kidney, and skin induced by D-gal and its effect was not less than that of the well-known L-ascorbic acid (VC) and α-tocopherol (VE). Overall, EAE is a potent natural antiaging agent with great antioxidant activity, which can be developed as a new medicine and cosmetic for the treatment of age-related conditions.