Search

Facilitating equilibrium in the nitrogen cycle, electrochemical nitrate reduction (NitRR) to ammonia stands as a carbon‐free method for ammonia synthesis. Copper‐based catalysts, renowned for NitRR, face a hurdle in supplying sufficient hydrogen radicals (*H) for efficient hydrogenation of NitRR intermediates. Addressing this, NiMoO4 is leveraged as an excellent *H donor, synergistically coupling it with a copper‐based catalyst. The work introduces a high‐performance NiMoO4/CuO nanowire (NW)/Copper foam (CF) catalyst for NitRR, achieving a remarkable Faraday efficiency (FE) of 98.8% and a yield of 0.8221 mmol cm−2 h−1. Operating at −0.2 V versus reversible hydrogen electrode (vs RHE) in an H‐type electrolytic cell, the catalyst demonstrates exceptional stability over 20 h. Additionally, coupling NitRR with an air stripping process enables efficient collection of NH4Cl products, offering a practical avenue for converting waste nitrates into valuable ammonia products. In‐depth in situ electrochemistry and density‐functional theory (DFT) calculations affirm the transformation of CuO into Cu/Cu2O during the electrocatalytic reduction process. Cu/Cu2O catalyzes nitrate conversion to nitrite, while NiMoO4, serving as a *H donor, facilitates deoxidation and hydrogenation of other N intermediates on the Cu/Cu2O surface, effectively driving the reduction of nitrate to ammonia. [ABSTRACT FROM AUTHOR]

δ‐MnO2 has been vigorously developed as an ideal cathode material for rechargeable aqueous zinc‐ion batteries (AZIBs) due to its spacious layer spacing suitable for ion storage. However, poor intrinsic conductivity, structural collapse, and sluggish reaction kinetics are major limitations restricting their battery performance. Doping engineering has been proven to be an effective strategy for modifying the structure, conductivity, and electronic properties of Mn‐based oxides. Here, a series of δ‐MnO2 hierarchical flowers with different cerium‐doped sites are proposed as high‐performance cathodes for AZIBs, revealing the effects of various Ce doping sites on the MnO2 layer‐by‐layer structure and battery performance. Chemical analysis and theoretical calculations indicate that δ‐MnO2 with both in‐layer and interlayer Ce doping (Cein/inter‐MnO2) allows for sufficient Zn2+ storage sites, higher conductivity, and enhanced reaction kinetics due to enlarged interlayer spacing, increased oxygen defects, and reduced Coulombic repulsion between zinc ions and manganese oxide hosts. As a result, Cein/inter‐MnO2 with extended ion transfer channels and sturdy structure delivers a superior capacity of 348.8 mAh g−1 at a current density of 300 mA g−1 over 100 cycles, and a high retention rate of ≈100% at a current density of 3000 mA g−1 over 2000 cycles. [ABSTRACT FROM AUTHOR]

Transition-metal selenides are considered promising anode materials for sodium-ion batteries due to their high theoretical capacity based on multielectron conversion reactions. However, their low intrinsic electrical conductivity and severe volume variations result in poor cycling performance and rate capability. Herein, a composite material of urchin-like hierarchical spheres in which FeSe2 embedded in TiN/C covered by in situ grown carbon nanotubes (denoted as FeSe2@TiN/C@CNTs) was designed and fabricated using a facile sol–gel, carbonization, and selenization process. The carbon matrix can disperse FeSe2 to prevent serious agglomeration, while TiN and CNTs could enhance the electrical conductivity of the composites. Additionally, TiN, carbon, and CNTs can buffer volume expansion during the charge/discharge process. Benefiting from the synergistic effects of FeSe2, carbon, TiN, and CNTs, the hybrid urchin-like FeSe2@TiN/C@CNTs spheres exhibit excellent cycling stability and ultrafast pseudocapacitive sodium-ion storage capability. The FeSe2@TiN/C@CNTs electrode delivers reversible capacity of 343.5 mA h g−1 at 200 mA g−1 for 1000 cycles, and a rate capability of 262.5 mA h g−1 at a high current density of 2 A g−1. Supported by the detailed kinetic analysis, the superior sodium-ion storage performance is attributed to the fast charge transfer rate and pseudocapacitive sodium-ion storage mechanism. Therefore, this work is expected to provide valuable insights for the rational design of metal-based compounds towards advanced metal-ion storage materials. [ABSTRACT FROM AUTHOR]