The controllable synthesis of NiO/Ni/C nanosheets via pulsed plasma in ethylene glycol solution for oxygen evolution electrocatalysis.

NiO-based composites exhibit high catalytic activity for the oxygen evolution reaction (OER). Herein, high-performance NiO/Ni/C nanosheet catalysts were obtained by liquid-phase pulsed plasma (LPP), which was generated between two nickel electrodes in ethylene glycol (EG) solution by a homemade high-voltage pulse power supply. Melted nickel nanodrops were ejected from nickel electrodes which were bombarded by the energetic plasma. Simultaneously, high-temperature nickel nanodrops promoted the decomposition of the organics which were converted in the EG solution by the catalysis of LPP and formed hierarchical porous carbon nanosheets. Due to the high surface energy of the hierarchical porous carbon nanosheets, the spherical particles of Ni/NiO were adsorbed on the surface to compose the NiO/Ni/C composites. The pore size distribution of the composites could be controlled with different EG concentrations. When the EG concentration was 10 vol% (EG30), the composites possessed a H2 + H2 + H3 type pore size distribution and maximum active site area, leading to an exceptional OER activity (289.2 mV overpotential at 10 mA cm-2).

SiC/Graphene Film by Laser CVD as an Implantable Sensor Material for Dopamine Detection.

Implantable electrochemical sensor holds great promise in the real-time monitoring of dopamine (DA) to regulate body function. However, the real application of these sensors is limited by the weak current signal of DA in the human body and the poor compatibility of the on-chip microelectronic devices. In this work, a SiC/graphene composite film was fabricated using laser chemical vapor deposition (LCVD) and employed as a DA sensor. The graphene in the porous nanoforest-like SiC framework offered efficient channels for electronic transmission, leading to an enhanced electron transfer rate and consequently an increased current response for DA detection. The three-dimensional (3D) porous network also facilitated the exposure of more catalytic active sites toward DA oxidation. Besides, the wide distribution of graphene in the nanoforest-like SiC films reduced the interfacial resistance of the charge transfer. The SiC/graphene composite film exhibited excellent electrocatalytic activity toward DA oxidation with a low detection limit of 0.11 µM and a high sensitivity of 0.86 µA·µM-1·cm-2. The film electrode also showed a wide linear response for DA in 0.5-78 µM, along with good selectivity, repeatability, and reproducibility. Furthermore, the cell counting kit-8 (CCK-8) and live-dead assays revealed that the film is also biocompatible for biomedical applications. Therefore, the nanoforest-like SiC/graphene composite film via the CVD process enables a promising candidate for an integrated miniature DA biosensor with high detection performance.

Phase-Selective Synthesis of Mo-Ta-C Ternary Nanosheets by Precisely Tailoring Mo/Ta Atom Ratio on Liquid Copper.

Phase-selective synthesis is an effective way to expand the ultra-thin transition metal carbide family and tune its properties. Herein, a chemical vapor deposition route with specially designed substrate (Ta wire-Cu foil-Mo foil) is carried out to synthesize Mo-Ta-C ternary nanosheets with tunable phase structure. The Ta atoms diffuse on the surface of liquid copper and Mo atoms diffuse through the liquid copper to the surface, which react with the carbon atoms decomposed from the methane and form the Mo-Ta-C ternary nanosheets. By precisely tailoring the Mo/Ta ratio and growth temperature, ultrathin layered orthorhombic (Mo2/3Ta1/3)2C nanosheets and non-layered cubic (Mo0.13Ta0.87) C nanosheets with thickness of 21 and 4 nm are selectively synthesized. The approach could pave the way for the formation of multi-component carbide nanosheets with controllable phases.

One-step chemical vapor deposition fabrication of Ni@NiO@graphite nanoparticles for the oxygen evolution reaction of water splitting.

NiO combined with conductive materials is a practicable way to improve its catalytic property for the oxygen evolution reaction (OER) by enhancing its electrical conductivity. Herein, Ni@NiO@graphite nanoparticles less than 20 nm in average diameter were synthesized by a one-step chemical vapor deposition process. Due to the deliberately controlled lack of oxygen, Ni particles and carbon clusters decomposed from NiCp2 precursors were oxidized incompletely and formed Ni@NiO core-shell nanoparticles coated by a graphite layer. The thickness of the graphite layer and the content of Ni were controlled by varying deposition temperature. The electrochemical activity towards the oxygen evolution reaction was assessed within alkaline media. Compared with commercial NiO powder, the Ni@NiO@graphite nanoparticles with the unique core-shell microstructure exhibit excellent OER performance, i.e., an overpotential of 330 mV (vs. RHE) at 10 mA cm-2 and a Tafel slope of 49 mV dec-1, due to the improved electrical conductivity and more active sites. This work provides a facile and rapid strategy to produce nanoparticles with unique microstructures as highly active electrocatalysts for the OER.

A high-throughput synthesis of large-sized single-crystal hexagonal boron nitride on a Cu-Ni gradient enclosure.

Large monolayer two-dimensional h-BN can be employed in novel electronic devices because of its thin insulation, excellent thermal stability, and high mechanical strength. However, the efficient synthesis of an h-BN film with large lateral size still faces a great challenge. Here, we report a method for the high-throughput synthesis of large-sized single-crystal h-BN on a Cu-Ni gradient alloy enclosure as the substrate via a low-pressure chemical vapor deposition (LPCVD) method. By depositing Ni on the Cu foil in different concentrations to obtain a Cu-Ni in-plane gradient concentration alloy enclosure, the highest growth rate of h-BN was 1 µm min-1 with the lateral size of h-BN being higher than 60 µm. Furthermore, the effect of the Ni content on the single crystal h-BN grain size and nucleation density and the mechanisms for the growth of h-BN were also investigated.