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Electrochemical synthesis of NH3 is a carbon‐free alternative to the traditional Haber–Bosch process. Obtaining NH3 from environmental pollutants, such as nitrates or nitrites, is a more practical route than from the nitrogen reduction reaction (NRR) due to the difficult cleavage of the inert triple bond of nitrogen gas. Here, a novel heterogeneous catalyst is reported based on iron (Fe) single‐atoms supported on 2D MoS2 (Fe‐MoS2) for the nitrate reduction reaction (NO3RR). Fe‐MoS2 exhibits remarkable performance with a maximum Faradaic efficiency of 98% for NO3RR to NH3 at an onset potential of −0.48 V versus the reversible hydrogen electrode (RHE) as confirmed by the isotopic nuclear magnetic resonance (NMR) analyses. Density functional theory (DFT) calculations reveal that the enhanced selectivity for the production of NH3 from single Fe atoms supported on MoS2 is attributed to a reduced energy barrier of 0.38 eV associated with de‐oxidation of *NO to *N. The catalysts are coupled to an InGaP/GaAs/Ge triple‐junction solar cell to demonstrate a solar‐to‐ammonia (STA) conversion efficiency of 3.4% and a yield rate of 510 µg h−1 cm−2. The results open new avenues for the design of single‐atom catalysts (SAC) for the realization of solar‐driven ammonia production. [ABSTRACT FROM AUTHOR]

The conversion of CO2 into desirable multicarbon products via the electrochemical reduction reaction holds promise to achieve a circular carbon economy. Here, we report a strategy in which we modify the surface of bimetallic silver-copper catalyst with aromatic heterocycles such as thiadiazole and triazole derivatives to increase the conversion of CO2 into hydrocarbon molecules. By combining operando Raman and X-ray absorption spectroscopy with electrocatalytic measurements and analysis of the reaction products, we identified that the electron withdrawing nature of functional groups orients the reaction pathway towards the production of C2+ species (ethanol and ethylene) and enhances the reaction rate on the surface of the catalyst by adjusting the electronic state of surface copper atoms. As a result, we achieve a high Faradaic efficiency for the C2+ formation of ≈80% and full-cell energy efficiency of 20.3% with a specific current density of 261.4 mA cm−2 for C2+ products. Strategies to systematically tune CO2 electroreduction to multicarbon products are of high interests. Here the authors report electron withdrawing functional group alters the reaction pathway towards C2+ products by adjusting the oxidation state of surface copper. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thicknesses of about 1 and 2 µm for alumina and Mn-Cu layers were observed. • The migration of alumina and Mn-Cu in fresh and used catalysts was observed. • AlO(OH) is formed in the presence of H 2 O (l) or H 2 O (g) , and it easily migrates. • STEM-EDX and SR-EELS showed Mn/(Mn + Cu) average values similar to the theoretical ones. • MnOx, Mn-Cu mixed oxide and CuO were identified by HRTEM-HAADF and SR-EELS. The texture, structure, composition, and electronic state of new and used monolithic Mn-Cu catalysts were studied. Characterisation was performed at different scales and spatial resolution by combining STEM-FIB and imaging techniques (STEM-HAADF) and spectroscopy (STEM-EDX and EELS of space resolution). A thickness of the alumina layer that varies between 1 and 2 µm was observed, while the thickness of the Mn-Cu catalyst layer varies linearly with the number of charges between 1 µm and 2 µm, for 1 and 2 charges, respectively. In both fresh and used catalysts, the migration of both phases was observed to a different extent, depending on the number of charges of the Mn-Cu phase. This was associated with the synthesis conditions or the catalytic behaviour in the combustion of the n -hexane. The STEM-EDX analyses showed a homogeneous distribution of Mn and Cu, with values like the theoretical one. At the nanoscale, the SR-EELS analyses detected the presence of nanometric patches with lower Cu content, chemically inhomogeneous with a higher Mn oxidation state than the rest of the material. The advanced characterisation techniques used in this work allowed the precise identification of part of the constitutive phases of the Mn-Cu system generated in-situ on the monolith. Among them, manganese oxides with different oxidation states (MnO, Mn 3 O 4 , Mn 2 O 3), Mn 3 Cu 3 O 8 and CuO were detected. [ABSTRACT FROM AUTHOR]