Enhanced Sodium-Ion Mobility and Electronic Transport of Hydrogen-Incorporated V₂O₅ Electrode Materials

Although α-V₂O₅ as an attractive electrode material for electrochemical energy storage devices exhibits a high theoretical capacity, its atomic structure with the confined size of channels for Na-ion transport and low electronic conductivity lead to the poor rate performance. Here we demonstrate that hydrogen incorporation in α-V₂O₅ is an effective way to improve the kinetics of ionic and electronic transports by using the density functional theory. Among various structures of hydrogen-incorporated α-V₂O₅, H₂V₂O₅ presents enlarged diffusion channels along the [010] and [001] directions where the diffusion energy barriers decrease to 0.844 eV (−34.93%) and 1.737 eV (−41.81%), respectively. Improved electronic conductivity is also achieved for H₂V₂O₅ due to the insulator–metal transition attributed by the high concentration of hydrogen atoms. As H₂V₂O₅ has smaller volume expansion occurring during the Na-intercalation process, H₂V₂O₅ at the comparable specific capacity exhibits higher rate capability and cyclability than α-V₂O₅

Self-Grown Ni(OH)₂ Layer on Bimodal Nanoporous AuNi Alloys for Enhanced Electrocatalytic Activity and Stability

Au nanostructures as catalysts toward electrooxidation of small molecules generally suffer from ultralow surface adsorption capability and stability. Here, we report Ni­(OH)₂ layer decorated nanoporous (NP) AuNi alloys with a three-dimensional and bimodal porous architecture, which are facilely fabricated by a combination of chemical dealloying and in situ surface segregation, for the enhanced electrocatalytic performance in biosensors. As a result of the self-grown Ni­(OH)₂ on the AuNi alloys with a coherent interface, which not only enhances adsorption energy of Au and electron transfer of AuNi/Ni­(OH)₂ but also prohibits the surface diffusion of Au atoms, the NP composites are enlisted to exhibit significant enhancement in both electrocatalytic activity and stability toward glucose electrooxidation. The highly reliable glucose biosensing with exceptional reproducibility and selectivity as well as quick response makes it a promising candidate as electrode materials for the application in nonenzymatic glucose biosensors

Dendritic, Transferable, Strictly Monolayer MoS₂ Flakes Synthesized on SrTiO₃ Single Crystals for Efficient Electrocatalytic Applications

Controllable synthesis of macroscopically uniform, high-quality monolayer MoS₂ is crucial for harnessing its great potential in optoelectronics, electrocatalysis, and energy storage. To date, triangular MoS₂ single crystals or their polycrystalline aggregates have been synthesized on insulating substrates of SiO₂/Si, mica, sapphire, <i>etc.</i>, <i>via</i> portable chemical vapor deposition methods. Herein, we report a controllable synthesis of dendritic, strictly monolayer MoS₂ flakes possessing tunable degrees of fractal shape on a specific insulator, SrTiO₃. Interestingly, the dendritic monolayer MoS₂, characterized by abundant edges, can be transferred intact onto Au foil electrodes and serve as ideal electrocatalysts for hydrogen evolution reaction, reflected by a rather low Tafel slope of ∼73 mV/decade among CVD-grown two-dimensional MoS₂ flakes. In addition, we reveal that centimeter-scale uniform, strictly monolayer MoS₂ films consisting of relatively compact domains can also be obtained, offering insights into promising applications such as flexible energy conversion/harvesting and optoelectronics

Controllable Growth and Transfer of Monolayer MoS₂ on Au Foils and Its Potential Application in Hydrogen Evolution Reaction

Controllable synthesis of monolayer MoS₂ is essential for fulfilling the application potentials of MoS₂ in optoelectronics and valleytronics, <i>etc.</i> Herein, we report the scalable growth of high quality, domain size tunable (edge length from ∼200 nm to 50 μm), strictly monolayer MoS₂ flakes or even complete films on commercially available Au foils, <i>via</i> low pressure chemical vapor deposition method. The as-grown MoS₂ samples can be transferred onto arbitrary substrates like SiO₂/Si and quartz with a perfect preservation of the crystal quality, thus probably facilitating its versatile applications. Of particular interest, the nanosized triangular MoS₂ flakes on Au foils are proven to be excellent electrocatalysts for hydrogen evolution reaction, featured by a rather low Tafel slope (61 mV/decade) and a relative high exchange current density (38.1 μA/cm²). The excellent electron coupling between MoS₂ and Au foils is considered to account for the extraordinary hydrogen evolution reaction activity. Our work reports the synthesis of monolayer MoS₂ when introducing metal foils as substrates, and presents sound proof that monolayer MoS₂ assembled on a well selected electrode can manifest a hydrogen evolution reaction property comparable with that of nanoparticles or few-layer MoS₂ electrocatalysts