Hierarchical Core-Shell Co2 N/CoP Embedded in N, P-doped Carbon Nanotubes as Efficient Oxygen Reduction Reaction Catalysts for Zn-air Batteries.

Projecting a cost-effective and highly efficient electrocatalyst for the oxygen reaction reduction (ORR) counts a great deal for Zn-air batteries. Herein, a hierarchical core-shell ORR catalyst (Co2 N/CoP@PNCNTs) is developed by embedding cobalt phosphides and/or cobalt nitrides as the core into N, P-doped carbon nanotubes (PNCNTs) as the shell via one-step carbonization, nitridation, and phosphorization of pyrolyzing Co-MOF precursor. The globally N, P-doped structure of Co2 N/CoP@PNCNTs demonstrates an outstanding electrocatalytic activity in the alkaline solution with the onset and half-wave potentials of 1.07 and 0.85 V respectively. Moreover, a Zn-air battery assembled from Co2 N/CoP@PNCNTs as the air cathode delivers an open circuit potential of 1.49 V, a maximum power density of 151.1 mW cm-2 and a specific capacity of 823.8 mAh kg-1 . It is reflected that Co2 N/CoP@PNCNTs provides a long-term durability with a slight decline of 15 h in the chronoamperometry measurement and an excellent charge-discharge stability with negligible voltage decay for 150 h at 10 mA cm-2 in Zn-air batteries. The results reveal that Co2 N/CoP@PNCNTs has superiority over most Co-Nx -C or Cox P@C catalysts reported so far. The excellent catalytic properties and stability of Co2 N/CoP@PNCNTs derive from synergistic effects between Co2 N/CoP and mesoporous N, P-doped carbon nanotubes.

Activity Promotion of Core and Shell in Multifunctional Core-Shell Co2 P@NC Electrocatalyst by Secondary Metal Doping for Water Electrolysis and Zn-Air Batteries.

Developing cost-efficient multifunctional electrocatalysts is highly critical for the integrated electrochemical energy-conversion systems such as water electrolysis based on hydrogen/oxygen evolution reactions (HER/OER) and metal-air batteries based on OER/oxygen reduction reactions (ORR). The core-shell structured materials with transition metal phosphide as the core and nitrogen-doped carbon (NC) as the shell have been known as promising HER electrocatalysts. However, their oxygen-related electrocatalytic activities still remain unsatisfactory, which severely limits their further applications. Herein an effective strategy to improve the core and shell performances of core-shell Co2 P@NC electrocatalysts through secondary metal (e.g., Fe, Ni, Mo, Al, Mn) doping (termed M-Co2 P@M-N-C) is reported. The as-synthesized M-Co2 P@M-N-C electrocatalysts show multifunctional HER/OER/ORR activities and good integrated capabilities for overall water splitting and Zn-air batteries. Among the M-Co2 P@M-N-C catalysts, Fe-Co2 P@Fe-N-C electrocatalyst exhibits the best catalytic activities, which is closely related to the configuration of highly active species (Fe-doping Co2 P core and Fe-N-C shell) and their subtle synergy, and a stable carbon shell for outstanding durability. Combination of electrochemical-based in situ Fourier transform infrared spectroscopy with extensive experimental investigation provides deep insights into the origin of the activity and the underlying electrocatalytic mechanisms at the molecular level.

Mo and Zn-Dual doped CuxO nanocrystals confined High-Conductive Cu arrays as novel sensitive sensor for neurotransmitter detection.

The development of sensitive and selective sensors using facile and low-cost methods for detecting neurotransmitter molecules is a critical factor in the health care system in regard to early diagnosis. In this research, an electrocatalyst derived from Mo,Zn dual-doped CuxO nanocrystals-based layer coating over one-dimensional copper nanowire arrays (Mo,Zn-CuxO/CuNWs) was successfully designed using a facile electrodeposition approach and used as an electrochemical sensor for non-enzymatic dopamine (DA) neurotransmitter detection. The synergistic effect caused by the dual-doping effect along with its excellent conductivity produced a large electroactive surface area and an improved hetero-charge transfer, thereby boosting DA sensing ability with a low limit detection of 0.32 µM, wide-range of detection (0.5 µM - 3.9 mM), long-term stability (5 weeks), and high selectivity in phosphate buffer solution (pH 7.4). Also, the sensor accurately determined DA in real blood serum-spiked solutions. The achieved results evidenced that the Mo,Zn-CuxO/CuNWs derived sensor is highly suitable for DA detection. Therefore, it also opens new windows for the development of low-cost, accurate, high-performance, and stable sensors for other neurotransmitter sensing for the purposes of better health care and early diagnosis.