Electrochemical nitrogen reduction reaction (NRR) as a new strategy for synthesizing ammonia has attracted ever‐growing attention, due to its renewability, flexibility, and sustainability. However, the lack of efficient electrocatalysts has hampered the development of such reactions. Herein, a series of amorphous Sn/crystalline SnS2 (Sn/SnS2) nanosheets by an L‐cysteine‐based hydrothermal process, followed by in situ electrochemical reduction, are synthesized. The amount of reduced amorphous Sn can be adjusted by selecting electrolytes with different pH values. The optimized Sn/SnS2 catalyst can achieve a high ammonia yield of 23.8 µg h−1 mg−1, outperforming most reported noble‐metal NRR electrocatalysts. According to the electrochemical tests, the conversion of SnS2 to an amorphous Sn phase leads to the substantial increase of its catalytic activity, while the amorphous Sn is identified as the active phase. These results provide a guideline for a rational design of low‐cost and highly active Sn‐based catalysts thus paving a wider path for NRR.

2 Two-dimensional (2D) materials and their heterostructures, with wafer-scale synthesis methods and fascinating properties, have attracted numerous interest and triggered revolutions of corresponding device applications. However, facile methods to realize accurate, intelligent and large-area characterizations of these 2D structures are still highly desired. Here, we report a successful application of machine-learning strategy in the optical identification of 2D structure. The machine-learning optical identification method (MOI method) endows optical microscopy with intelligent insight into the characteristic colour information in the optical photograph. Experimental results indicate that the MOI method enables accurate, intelligent and large-area characterizations of graphene, molybdenum disulphide (MoS2) and their heterostructures, including identifications of the thickness, the existence of impurities, and even the stacking order. Thanks to the convergence of artificial intelligence and nanoscience, this intelligent identification method can certainly promote the fundamental research and wafer-scale device application of 2D structures.

Production of efficient and cost-effective metal-based catalysts for electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions is quite challenging. In this work, metal bismuth (Bi) nanosheets with a single-crystalline structure supported on a carbon fiber paper were prepared through the in situ electrocatalytic topotactic transformation of bismuth iodide oxide nanosheets. These Bi nanosheets can be used as efficient non-noble metal catalysts for NRR, achieving an NH3 yield of 12.49 μg h–1 mgcat. –1 and a high faradaic efficiency of 7.09%. Density functional theory calculations reveal that although the basal plane of Bi nanosheets is relatively inert, the exposed edge sites are conductive to the adsorption and activation of N2 molecules. This work presents the significance of using the topotactic transformation strategy for NRR and provides an inspiration for the development of efficient metal-based catalysts.

Solar energy is considered as a green and abundant energy for catalytic reactions. In this work, a magnetically recoverable NiFe2O4/2D MoS2–Pd nanocomposite is successfully synthesized via a simple one-pot hydrothermal method. The intimate interfacial contact between NiFe2O4 nanocubes and corrugated MoS2 nanosheets forms the NiFe2O4/2D MoS2 p-n heterojunction, while plasmonic Pd nanoparticles are uniformly immobilized on the surface of it. Dye degradation and Suzuki-Miyaura coupling reaction are employed to evaluate the photocatalytic activity of the NiFe2O4/2D MoS2–Pd nanocomposite. Significantly, both dye degradation and Suzuki-Miyaura coupling reaction can be efficiently performed in a short time under mild conditions. In comparison, the physically mixed NiFe2O4+2D MoS2 heterojunction immobilizing palladium nanoparticles shows poor photocatalytic activity. Photocatalytic results demonstrate that the in situ formation of NiFe2O4/2D MoS2 p-n heterojunction greatly improves the visible-light absorption and facilitates the transferring of photogenerated electrons and holes. Moreover, Pd nanoparticles as the electron reservoirs can further suppress the electron–hole recombination and enhance the photocatalytic activity. The construction of semiconductive p-n heterojunction to immobilize metal nanocatalysts will be an inspiration for other useful photocatalytic applications.

Electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions is emerging as a potential alternative to the Haber–Bosch process when cost and environmental protection are considered. Furthermore, the grand challenge on N2 activation encourages development of efficient NRR catalysts. Herein, we report the positive effect of oxygen vacancies in Ta2O5 nanorods for effective N2 reduction. Density functional theory calculations reveal that N2 can be efficiently activated at the O-vacancy site via coordination with two Ta atoms adjacent to the O-vacancy. Electrocatalytic NRR experiments verify the superior catalytic performance of O-vacancy-engineered Ta2O5 nanorods (NH3 yield, 15.9 μg h–1 mg–1 cat; Faradaic efficiency, 8.9%). This work clearly demonstrates the significance of defect engineering on the NRR field.