Nano-Cu Derived from a Copper Nitride Precatalyst for Reductive Coupling of Nitroaromatics to Azo Compounds

The study of structural reconstruction is vital for the understanding of the real active sites in heterogeneous catalysis and guiding the improved catalyst design. Herein, we applied a copper nitride precatalyst in the nitroarene reductive coupling reaction and made a systematic investigation on the dynamic structural evolution behaviors and catalytic performance. This Cu3N precatalyst undergoes a rapid phase transition to nanostructured Cu with rich defective sites, which act as the actual catalytic sites for the coupling process. The nitride-derived defective Cu is very active and selective for azo formation, with 99.6% conversion of nitrobenzene and 97.1% selectivity to azobenzene obtained under mild reaction conditions. Density functional theory calculations suggest that the defective Cu sites play a role for the preferential adsorption of nitrosobenzene intermediates and significantly lowered the activation energy of the key coupling step. This work not only proposes a highly efficient noble-metal-free catalyst for nitroarenes coupling to valuable azo products but also may inspire more scientific interest in the study of the dynamic evolution of metal nitrides in different catalytic reactions

Integrated Flexible Electrode for Oxygen Evolution Reaction: Layered Double Hydroxide Coupled with Single-Walled Carbon Nanotubes Film

The integration of active components and conductive supports forming free-standing electrodes is highly desirable for a series of energy storage and conversion devices. Herein, a facile hydrothermal method is developed to achieve the coupling of NiFe layered double hydroxide (LDH) and single-walled carbon nanotubes (SWNT) film, forming an integrated flexible electrode for oxygen evolution reaction (OER). The electrode requires a low overpotential of 250 mV to reach a current density of 10 mA cm^–2 in 1 M KOH, and shows rapid reaction kinetics with a Tafel slope of 35 mV dec^–1. Advanced soft X-ray absorption near-edge structure measurements efficiently indicate strong interfacial electron coupling between the LDH and SWNT, which authentically contributes to superior OER performance. This work provides a new strategy to design binder-free and flexile electrodes for practical application

Engineering the Electronic Structure of MoS₂ Nanorods by N and Mn Dopants for Ultra-Efficient Hydrogen Production

Developing economical and efficient electrocatalysts with nonprecious metals for the hydrogen evolution reaction (HER), especially in water-alkaline electrolyzers, is pivotal for large-scale hydrogen production. Recently, both density functional theory (DFT) calculations and experimental studies have demonstrated that earth-abundant MoS₂ is a promising HER electrocatalyst in acidic solution. However, the HER kinetics of MoS₂ in alkaline solution still suffer from a high overpotential (90–220 mV at a current density of 10 mA cm^–2). Herein, we report a combined experimental and first-principle approach toward achieving an economical and ultraefficient MoS₂-based electrocatalyst for the HER by fine-tuning the electronic structure of MoS₂ nanorods with N and Mn dopants. The developed N,Mn codoped MoS₂ catalyst exhibits an outstanding HER performance with overpotentials of 66 and 70 mV at 10 mA cm^–2 in alkaline and phosphate-buffered saline media, respectively, and corresponding Tafel slopes of 50 and 65 mV dec^–1. Moreover, the catalyst also exhibits long-term stability in HER tests. DFT calculations suggest that (1) the electrocatalytic performance can be attributed to the enhanced conductivity and optimized electronic structures for facilitating H* adsorption and desorption after N and Mn codoping and (2) N and Mn dopants can greatly activate the catalytic HER activity of the S-edge for MoS₂. The discovery of a simple approach toward the synthesis of highly active and low-cost MoS₂-based electrocatalysts in both alkaline and neutral electrolytes allows the premise of scalable production of hydrogen fuels

Facile Synthesis of Hierarchical Cu₂MoS₄ Hollow Sphere/Reduced Graphene Oxide Composites with Enhanced Photocatalytic Performance

We present a controllable synthesis of ternary hierarchical hollow sphere, assembling by numerous particle-like Cu₂MoS₄, via a facile hydrothermal method. By adding graphene oxides (GO) in the reaction process, Cu₂MoS₄/reduced graphene oxide (RGO) heterostructures were obtained with enhanced photocurrent and photocatalytic performance. As demonstrated by electron microscopy observations and X-ray characterizations, considerable interfacial contact was achieved between hierarchical Cu₂MoS₄ hollow sphere and RGO, which could facilitate the separation of photoinduced electrons and holes within the hybrid structure. In comparison with the pure Cu₂MoS₄ hollow sphere, the obtained hybrid structures exhibited significantly enhanced light absorption property and the ability of suppressing the photoinduced electron–holes recombination, which led to significant enhancement in both photocurrent and efficiency of photocatalytic methyl orange (MO) degradation under visible light (λ > 420 nm) irradiation