Vertically Aligned NiCo2O4 Nanosheet-Encapsulated Carbon Fibers as a Self-Supported Electrode for Superior Li+ Storage Performance

Synthesis of Co/CeO2 hetero-particles with abundant oxygen-vacancies supported by carbon aerogels for ORR and OER

It is highly significant for the fabrication of rechargeable metal-air batteries to develop cost-efficient and high-performance electrocatalysts of bifunctionality for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Herein, we demonstrate a hybrid composed of CeO₂-decorated Co nanoparticles supported on three-dimensionally porous carbon aerogels (Co-CeO₂/C aerogels) as a superior bifunctional electrocatalyst. The preparation of Co-CeO₂/C aerogels depends on the formation of a novel CeCl₃/K₃Co(CN)₆-chitosan (CS) hydrogel, during which the cyanide groups of K₃Co(CN)₆ combines the hydroxyls in CS by hydrogen bridges, accompanying with the substitution of chloride groups in CeCl₃ by cyanide groups in K₃Co(CN)₆. The electron spin resonance offers a convincing proof that numerous oxygen vacancies were found in Co-CeO₂/C aerogels after the introduction of CeO₂. The developed Co-CeO₂/C aerogels showed an outstanding electrochemical performance for both OER and ORR in comparsion with RuO₂ and Pt/C catalysts in 0.1 M KOH solution. A small overpotential (380 mV) and a low Tafel slope (99 mV dec^-1) were observed for OER, while the half-wave potential (0.75 V) and the onset potential (0.92 V) were high for ORR. The superior performance could be put down to the multihole heterostructure, multiple components and abundant oxygen vacancies. It was very helpful for the adsorption and the catalyzation of the reactants and the efficient mass transport of reagent/product. This work paves a neoteric method to synthesize a bifunctional hybrid catalyst with a highly efficient performance of energy conversion and storage.

Cyanogel-Derived Synthesis of Porous PdFe Nanohydrangeas as Electrocatalysts for Oxygen Reduction Reaction

It is important to develop cost-efficient electrocatalysts used in the oxygen reduction reaction (ORR) for widespread applications in fuel cells. Palladium (Pd) is a promising catalyst, due to its more abundant reserves and lower price than platinum (Pt), and doping an earth-abundant 3d-transition metal M into Pd to form Pd-M bimetallic alloys may not only further reduce the use of expensive Pd but also promote the electrocatalytic performance of ORR, owing to the synergistic effect between Pd and M. Here we report a cyanogel-derived synthesis of PdFe alloys with porous nanostructure via a simple coinstantaneous reduction reaction by using K2PdIICl4/K4FeII(CN)6 cyanogel as precursor. The synthesized PdFe alloys possess hydrangea-like morphology and porous nanostructure, which are beneficial to the electrochemical performance in ORR. The onset potential of the porous PdFe nanohydrangeas is determined to be 0.988 V, which is much more positive than that of commercial Pt/C catalyst (0.976 V) and Pd black catalyst (0.964 V). Resulting from the unique structural advantages and synergetic effect between bimetals, the synthesized PdFe nanohydrangeas with porous structure have outstanding electrocatalytic activity and stability for ORR, compared with the commercial Pd black and Pt/C.

Review on carbonaceous materials and metal composites in deformable electrodes for flexible lithium-ion batteries

With the rapid propagation of flexible electronic devices, flexible lithium-ion batteries (FLIBs) are emerging as the most promising energy supplier among all of the energy storage devices owing to their high energy and power densities with good cycling stability. As a key component of FLIBs, to date, researchers have tried to develop newly designed high-performance electrochemically and mechanically stable pliable electrodes. To synthesize better quality flexible electrodes, based on high conductivity and mechanical strength of carbonaceous materials and metals, several research studies have been conducted. Despite both materials-based electrodes demonstrating excellent electrochemical and mechanical performances in the laboratory experimental process, they cannot meet the expected demands of stable flexible electrodes with high energy density. After all, various significant issues associated with them need to be overcome, for instance, poor electrochemical performance, the rapid decay of the electrode architecture during deformation, and complicated as well as costly production processes thus limiting their expansive applications. Herein, the recent progression in the exploration of carbonaceous materials and metals based flexible electrode materials are summarized and discussed, with special focus on determining their relative electrochemical performance and structural stability based on recent advancement. Major factors for the future advancement of FLIBs in this field are also discussed.

Synthesis of NiCo2O4 Nanostructures and Their Electrochemial Properties for Glucose Detection

In this work, we prepared spinel-type NiCo2O4 (NCO) nanopowders as a low-cost and sensitive electrochemical sensor for nonenzymatic glucose detection. A facile and simple chemical bath method to synthesize the NCO nanopowders is demonstrated. The effect of pH and annealing temperature on the formation mechanism of NCO nanoparticles was systematically investigated. Our studies show that different pHs of the precursor solution during synthesis result in different intermediate phases and relating chemical reactions for the formation of NCO nanoparticles. Different morphologies of the NCO depending on pHs are also discussed based on the mechanism of growth. Electrochemical performance of the prepared NCO was characterized towards glucose, which reveals that sensitivity and selectivity of the NCO are significantly related with the final microstructure combined with constituent species with multiple oxidation states in the spinel structure.

Morphology restrained growth of V2O5 by the oxidation of V-MXenes as a fast diffusion controlled cathode material for aqueous zinc ion batteries

Restrained morphology and structural engineering of layered V₂O₅ by the oxidation of V-MXene to form a unique V₂O₅@V₂C nanohybrids at different temperature and used as a cathode material for aqueous Zn-ion batteries (ZIBs).