NiCo Alloy Nanoparticles on a N/C Dual-Doped Matrix as a Cathode Catalyst for Improved Microbial Fuel Cell Performance

CoNi Alloys Encapsulated in N-Doped Carbon Nanotubes for Stabilizing Oxygen Electrocatalysis in Zinc-Air Battery

Alloy-based catalysts with high corrosion resistance and less self-aggregation are essential for oxygen reduction/evolution reactions (ORR/OER). Here, via an in situ growth strategy, NiCo alloy-inserted nitrogen-doped carbon nanotubes were assembled on a three-dimensional hollow nanosphere (NiCo@NCNTs/HN) using dicyandiamide. NiCo@NCNTs/HN exhibited better ORR activity (half-wave potential (E_1/2) of 0.87 V) and stability (E_1/2 shift of only -13 mV after 5000 cycles) than commercial Pt/C. NiCo@NCNTs/HN displayed a lower OER overpotential (330 mV) than RuO₂ (390 mV). The NiCo@NCNTs/HN-assembled zinc-air battery exhibited high specific-capacity (847.01 mA h g^-1) and cycling-stability (291 h). Synergies between NiCo alloys and NCNTs facilitated the charge transfer to promote 4e^- ORR/OER kinetics. The carbon skeleton inhibited the corrosion of NiCo alloys from surface to subsurface, while inner cavities of CNTs confined particle growth and the aggregation of NiCo alloys to stabilize bifunctional activity. This provides a viable strategy for the design of alloy-based catalysts with confined grain-size and good structural/catalytic stabilities in oxygen electrocatalysis.

Molten salt synthesis of NiCo-NiCo2O4@C nanotubes as anode materials for Li-ion batteries

The construction of carbon-encapsulated transition metal nanotube structures is a preferred method that can effectively slow down volume expansion, improve cycling stability and enhance the electrical conductivity of the reactive sites of lithium-ion batteries. In this study, nanotubes of carbon-coated NiCo-NiCo₂O₄ nanoparticles (NC-NCO@C) were prepared by a one-step molten salt method at high temperature using Ni and Co as catalytic centers and sodium acetate as carbon source. We used NC-NCO@C-2 nanotubes as anode materials for lithium-ion batteries(LIBs), which exhibited excellent lithium storage performance and good stability, with a specific capacity of 616.26 mAh g^-1 after 1000 cycles at a high current density of 1 A g^-1. In addition, NC-NCO@C-2 were used as anodes in lithium-ion full cells and LiFePO₄ (LFP) was used as the cathode. The NC-NCO@C-2//LFP full-cell exhibits high capacity and good cycling stability, with a capacity of 100.7 mAh g^-1 after 100 cycles and a capacity retention rate of 92%. The construction of NC, NCO, and carbon ternary complexes was found to activate and promote the reversible conversion of certain inorganic components at the solid electrolyte interfaces (SEI), which effectively reduced the volume change during cycling, increased the electrical conductivity, and improved the cycling stability of the electrode. The proposed one-step molten salt synthesis of Carbon-coated metals complexes with excellent compatibility characteristics, is expected to solve the problem of volume change in transition metals, which is encountered in LIBs applications.

Improved bioelectrochemical performance of MnO2 nanorods modified cathode in microbial fuel cell

The property of cathode in the microbial fuel cell (MFC) was one of the key factors limiting its output performance. MnO₂ nanorods were prepared by a simple hydrothermal method as cathode catalysts for MFCs. There were a number of typical characteristic crystal planes of MnO₂ nanorods like (110), (310), (121), and (501). Additionally, there were great many hydroxyl groups on the surface of nanorod-like MnO₂, which provided a rich set of active adsorption sites. The maximum power density (P_max) of MnO₂-MFC was 180 mW/m², which was 1.51 times that of hydrothermally synthesized MnO₂ (119.07 mW/m²), 4.28 times that of naturally synthesized MnO₂ (42.05 mW/m²), and 5.61 times that of the bare cathode (32.11 mW/m²). The maximum voltage was 234 mV and the maximum stabilization time was 4 days. The characteristics of MnO₂, including rod-like structure, high specific surface area, and high conductivity, were conducive to providing more active sites for oxygen reduction reaction (ORR). Therefore, the air cathode modified by MnO₂ nanorods was a kind of fuel cell electrode with great application potential.