High Selenium Loading in Vertically Aligned Porous Carbon Framework with Visualized Fast Kinetics for Enhanced Lithium/Sodium Storage

Lithium/sodium–selenium (Li/Na–Se) batteries with high volumetric specific capacity are considered promising as next-generation battery technologies. However, their practical application is hindered by challenges such as low Se loading in cathodes and the polyselenides shuttle effect. To address these challenges, a new Se host is introduced in the form of a free-standing N, O co-doped vertically aligned porous carbon framework decorated with a carbon nanotube forest (VCF-CNTs), allowing for high mass loading of up to 16 mg cm−2. The low-tortuosity Se@VCF-CNTs architecture facilitates rapid lithiation/sodiation kinetics, while the CNT forests in vertical microchannels enhance efficient Se loading and serve as a multi-layer fence to prevent undesired polyselenide shuttling. Consequently, the Se@VCF-CNTs cathode displays a significant areal capacity of 10.3 mAh cm−2 at 0.1 C with a Se loading of 16 mg cm−2 for Li–Se batteries, exceeding that of commercial lithium ion batteries (4.0 mAh cm−2). In Na–Se batteries, the Se@VCF-CNTs electrode with a Se loading of 5 mg cm−2 exhibits a discharge capacity of 436 mAh g−1 after 200 cycles, proving its consistent cycling performance. This study enriches the field of knowledge concerning high-loading Se-based battery systems, offering a promising avenue for enhancing energy density in the field

The Role of Transition Metal and Nitrogen in Metal–N–C Composites for Hydrogen Evolution Reaction at Universal pHs

For the first time, we demonstrated that transition metal and nitrogen codoped carbon nanocomposites synthesized by pyrolysis and heat treatment showed excellent catalytic activity toward hydrogen evolution reaction (HER) in both acidic and alkaline media. The overpotential at 10 mA cm^–2 was 235 mV in a 0.5 M H₂SO₄ solution at a catalyst loading of 0.765 mg cm^–2 for Co–N–C. In a 1 M KOH solution, the overpotential was only slightly increased by 35 mV. The high activity and excellent durability (negligible loss after 1000 cycles in both acidic and alkaline media) make this carbon-based catalyst a promising alternative to noble metals for HER. Electrochemical and density functional theory (DFT) calculation results suggested that transition metals and nitrogen played a critical role in activity enhancement. The active sites for HER might be associated with metal/N/C moieties, which have been also proposed as reaction centers for oxygen reduction reaction

Polymer-Embedded Fabrication of Co₂P Nanoparticles Encapsulated in N,P-Doped Graphene for Hydrogen Generation

We developed a method to engineer well-distributed dicobalt phosphide (Co₂P) nanoparticles encapsulated in N,P-doped graphene (Co₂P@NPG) as electrocatalysts for hydrogen evolution reaction (HER). We fabricated such nanostructure by the absorption of initiator and functional monomers, including acrylamide and phytic acid on graphene oxides, followed by UV-initiated polymerization, then by adsorption of cobalt ions and finally calcination to form N,P-doped graphene structures. Our experimental results show significantly enhanced performance for such engineered nanostructures due to the synergistic effect from nanoparticles encapsulation and nitrogen and phosphorus doping on graphene structures. The obtained Co₂P@NPG modified cathode exhibits small overpotentials of only −45 mV at 1 mA cm^–2, respectively, with a low Tafel slope of 58 mV dec^–1 and high exchange current density of 0.21 mA cm^–2 in 0.5 M H₂SO₄. In addition, encapsulation by N,P-doped graphene effectively prevent nanoparticle from corrosion, exhibiting nearly unfading catalytic performance after 30 h testing. This versatile method also opens a door for unprecedented design and fabrication of novel low-cost metal phosphide electrocatalysts encapsulated by graphene

Regime-Dependence of Nocturnal Nitrate Formation via N2O5 Hydrolysis and Its Implication for Mitigating Nitrate Pollution

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