Exploiting S,N co-doped 3D hierarchical porous carbon with FeII–N4 moiety as an efficient cathode electrocatalyst for advanced Zn–air battery

CrS Doped MOF-Derived Carbon Implanted CoNi Particles as Exceedingly Effectual Oxygen Electrocatalysts in Sustainable Zinc-Air Batteries

Utilizing affordable bifunctional catalysts per strong ORR/OER (oxygen reduction and evolution reactions) ability and superior zinc-air battery performance is yet difficult due to the diverse mechanisms of ORR/OER. This work uses CoNi-MOF (metal-organic framework) as a self-template to yield the CrS doped CoNi/C bifunctional catalyst. Comparable to Pt/C and IrO2 commercial catalysts, the CrS@CoNi/C catalyst exhibits improved electrocatalytic activity toward OER and ORR due to its linked pellet architecture and intact metal sulfide@carbon structure. The CrS@CoNi/C catalyst has the most intriguing ORR/OER performance, with a significantly lower potential and an exceptionally extended cycle duration (E1/2 = 0.72 V and η10 = 260 mV). The CrS@CoNi/C-based aqueous zinc-air battery shows long-term charge-discharge stability (more than 100h/600 cycles) together with significant specific capacity (789.7 mAh g-1 Zn) and power density (132.2 mW cm-2). Most significantly, after charge-discharge stability, the recharged CrS@CoNi/C-based alkaline zinc-air battery has been employed to exhibit less structural deformation for the cathode and more zincate ion production for the anode side electrodes, which is employed through TEM analysis.

Noble-metal-free co-N-C catalyst derived from cellulose-based poly(ionic liquid)s for highly efficient oxygen reduction reaction

Noble-Metal-Free nitrogen-doped carbon-based materials are promising electrocatalysts for oxygen reduction reaction (ORR), yet it remains a great challenge to construct efficient porous non-noble metal nitrogen-doped carbon (M-N-C) catalysts with uniform distribution, due to the easy aggregation of metals. Herein, we reported the synthesis and assessment of a novel and efficient noble-metal-free catalyst for oxygen reduction reaction (ORR) from pyrolysis of a cobalt-containing cellulosic poly(ionic liquid) (Co-N-C). The prepared Co-N-C catalyst possesses high surface area, hierarchical porous structure, well-dispersed Co nanoparticles and large amounts of low-coordinated Co active sites. Especially, the Co-N-C-850 sample exhibits a high ORR activity (E_onset = 0.827 V, E_1/2 = 0.74 V) that can rival 20 wt% commercial Pt/C (E_onset = 0.833 V, E_1/2 = 0.71 V) in alkaline media. Moreover, the Co-N-C-850 sample also shows excellent anti-methanol poisoning activity and long-term stability toward ORR compared with commercial Pt/C. Our study provides a promising avenue both for the development of non-noble M-N-C catalysts for fuel cells and functional utilization of cellulose.

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.

Carbon Nanomaterials With Hollow Structures: A Mini-Review

Carbon nanomaterials with high electrical conductivity, good chemical, and mechanical stability have attracted increasing attentions and shown wide applications in recent years. In particularly, hollow carbon nanomaterials, which possess ultrahigh specific surface area, large surface-to-volume ratios, and controllable pore size distribution, will benefit to provide abundant active sites, and mass loading vacancy, accelerate electron/ion transfer as well as contribute to the specific density of energy storage systems. In this mini-review, we summarize the recent progresses of hollow carbon nanomaterials by focusing on the synthesis approaches and corresponding nanostructures, including template-free and hard-template carbon hollow structures, metal organic framework-based hollow carbon structures, bowl-like and cage-like structures, as well as hollow fibers. The design and synthesis strategies of these hollow carbon nanomaterials have been systematically discussed. Finally, the emerging challenges and future prospective for developing advanced hollow carbon structures were outlined.

Core–shell structured nanoporous N-doped carbon decorated with embedded Co nanoparticles as bifunctional oxygen electrocatalysts for rechargeable Zn–air batteries

Highly active core–shell structured PNC@CoNC was successfully prepared and used as an effective air–electrode catalyst in advanced Zn–air batteries.