Search

Summary: Exploring progressed activity and stability, electrocatalyst toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), has been the most considerable factor in extensive commercialization of metal‐air batteries and fuel cells. Herein, Co/N co‐doped 3D hierarchical porous bifunctional oxygen electrocatalyst was synthesized using F127 as soft template and PMMA nanosphere as hard template to build hierarchically ordered macro/mesoporous porous nanostructure. The as‐obtained macro/mesoporous Co‐N‐doped carbon endowing its 3D ordered hierarchical porosity and satisfactory surface area, leading to superior performance for ORR, OER, and rechargeable Zn‐air battery. For ORR, the catalyst showed superior ORR activity with an attractive half‐wave potential of 0.85 V (vs RHE), remarkable methanol tolerance, and robust long‐term stability under alkaline electrolyte. For OER, the as‐synthetized electrocatalyst exhibited low overpotential of 1.67 V (vs RHE) under the current density of 10 mA/cm2. Moreover, the Zn‐air battery assembled from the hierarchical porous catalyst displayed a high peak power density of 146 mW/cm2. [ABSTRACT FROM AUTHOR]

Developing high efficiency and durability catalysts for the electrocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is fundamental to achieve the large‐scale commercial application of fuel cells and metal‐air batteries. Herein, a series of Co−N doped bi‐functional hierarchical porous electrocatalysts were synthesized using polyvinyl pyrrolidone (PVP) as soft template to assist the Zn/Co bimetal Zeolitic Imidazolate Framework (BMZIF) to form micro‐/mesoporous carbon nanospheres via a convenient one‐step solution synthesis method, followed by pyrolysis to form carbon nanospheres catalysts. The as‐prepared Co/N co‐doped carbon exhibits outstanding performances in the ORR and OER due to the formed hierarchical pores architecture and the high surface area. The catalyst displays superior ORR performance with a high half‐wave potential of 0.89 V, and a remarkable long‐term stability in 0.1 M KOH. In addition, the electrocatalyst elicits a low voltage of 1.72 V under the current density of 10 mA cm−2. Moreover, the zinc‐air battery fabricated with P‐CNCo‐3 delivers a power density of 175.1 mW cm−2, a high specific capacity of 791 mAh g−1 and an energy density of 976 Wh kg−1 at 20 mA cm−2. [ABSTRACT FROM AUTHOR]

A novel method for the preparation of iron‐ and nitrogen‐codoped carbon nanotubes (Fe‐N‐CNTs) is proposed, based on the catalytic pyrolysis of waste plastics. First, carbon nanotubes are produced from pyrolysis of plastic waste over Fe‐Al2O3; then, Fe‐CNTs and melamine are heated together in an inert atmosphere. Different co‐pyrolysis temperatures are tested to optimize the electrocatalyst production. A high doping temperature improves the degree of graphite formation and promotes the conversion of nitrogen into a more stable form. Compared with commercial Pt/C, the electrocatalyst obtained from pyrolysis at 850 °C shows remarkable properties, with an onset potential of 0.943 V versus RHE and a half‐wave potential of 0.811 V versus RHE, and even better stability and anti‐poisoning properties. In addition, zinc–air battery tests are performed, and the optimized catalyst exhibits a high maximum power density. [ABSTRACT FROM AUTHOR]

Development of noble metal-free catalysts with great electrocatalytic performance and stability is of importance for electrochemical energy conversion and storage devices. Herein, we reported the synthesis of trifunctional catalysts with three-dimension (3D) hierarchically porous nitrogen-doped carbon framework with Ni-Co dual metal-involving and carbon nanotubes growth derived from nickel metal-organic framework. The as-synthesized catalyst exhibited better oxygen reduction reaction performance under both neutral and basic conditions compared with commercial Pt/C catalysts. Under basic electrolyte, the oxygen evolution reaction performance of the synthesized catalyst was comparable to that of commercial IrO 2 catalysts and reasonable hydrogen evolution activity was achieved compared with reported non-noble metal-based catalysts. The assembled microbial fuel cell using the as-prepared material as the air electrode exhibited a maximum power density of 1971.2 mW m−2 and could steadily operate for more than 250 h of feed period. Furthermore, the Zn-air battery fabricated with the obtained catalyst showed excellent power density and rechargeability, which were superior to that of a Zn-air battery using Pt/C/IrO 2 as the air electrode. We anticipate that the results described here can provide a new idea for design of multifunctional electrocatalysts for energy conversion and storage devices. [ABSTRACT FROM AUTHOR]