Electrocatalytic behaviour of Ni-base amorphous alloys

Recent Advances in Metallic Glass Nanostructures: Synthesis Strategies and Electrocatalytic Applications

Recent advances in metallic glass nanostructures (MGNs) are reported, covering a wide array of synthesis strategies, computational discovery, and design solutions that provide insight into distinct electrocatalytic applications. A brief introduction to the development and unique features of MGNs with an overview of top-down and bottom-up synthesis strategies is presented. Specifically, the morphology and structural analysis of several examples applying MGNs as electrodes are highlighted. Subsequently, a comprehensive discussion of commonly employed kinetic parameters and their connection with the unique material structures of MGNs on individual electrocatalytic reactions is made, including the hydrogen evolution reaction, oxygen reduction reaction, and alcohol (methanol or ethanol) oxidation reaction. Finally, a summary of the challenges and perspective on the future research and development relevant to MGNs as electrocatalysts is provided.

Binary Nickel-Cobalt Oxides Electrode Materials for High-Performance Supercapacitors: Influence of its Composition and Porous Nature

Nickel-cobalt oxides were prepared by coprecipitation of their hydroxides precursors and a following thermal treatment under a moderate temperature. The preformed nickel-cobalt bimetallic hydroxide exhibited a flower-like morphology with single crystalline nature and composed of many interconnected nanosheets. The ratio of Ni to Co in the oxides could easily be controlled by adjusting the composition of the original reactants for the preparation of hydroxide precursors. It was found that both the molecular ratio of Ni to Co and the annealing temperature had significant effects on their porous structure and electrochemical properties. The effect of the Ni/Co ratio on the pseudocapacitive properties of the binary oxide was investigated in this work. The binary metal oxide with the exact molar ratio of Ni:Co = 0.8:1 annealed at 300 °C, showing an optimum specific capacitance of 750 F/g. However, too high an annealing temperature would lead to a large crystal size, a low specific surface area, as well as a much lower pore volume. With the use of the binary metal oxide with Ni:Co = 0.8:1 and activated carbon as the positive and negative electrode, respectively, the assembled hybrid capacitor could exhibit a high-energy density of 34.9 Wh/kg at the power density of 875 W/kg and long cycling life (86.4% retention of the initial value after 10000 cycles).

Electrochemical performance of annealed cobalt-benzotriazole/CNTs catalysts towards the oxygen reduction reaction

One of the major limitations yet to the global implementation of polymer electrolyte membrane fuel cells (PEMFCs) is the cathode catalyst. The development of efficient platinum-free catalysts is the key issue to solve the problem of slow kinetics of the oxygen reduction reaction (ORR) and high cost. We report a promising catalyst for ORR prepared through the annealing treatment under inert conditions of the cobalt-benzotriazole (Co-BTA) complex supported on carbon nanotubes (CNTs). The N-rich benzotriazole precursor was chosen based on its ability to complex Co(II) ions and generate under annealing highly reactive radicals able to tune the physicochemical properties of CNTs. X-Ray photoelectron spectroscopy (XPS) was used to follow the surface structure changes and highlight the active electrocatalytic sites towards the ORR. To achieve further evaluation of the catalysts in acidic medium, voltamperometry, rotating disk electrode (RDE), rotating ring-disk electrode (RRDE) and half-cell measurements were performed. The resulting catalysts (Co/N/CNTs) all show catalytic activity towards the ORR, the most active one resulting from annealing at 700 °C. The overall electron transfer number for the catalyzed ORR was determined to be ∼3.7 with no change upon the catalyst loading, suggesting that the ORR was dominated by a 4e(-) transfer process. The results indicate a promising alternative cathode catalyst for ORR in fuel cells, although its performance is still lower (overpotential around 110 mV evaluated by RDE and RRDE) than the reference Pt/C catalyst.