Iron-nitrogen dual-doped three-dimensional mesoporous carbons for high-activity electrocatalytic oxygen reduction

Iron-nitrogen dual-doped three-dimensional mesoporous carbons for high-activity electrocatalytic oxygen reductio

Three-dimensional interconnected nitrogen-doped mesoporous carbons as active electrode materials for application in electrocatalytic oxygen reduction and supercapacitors

In this paper, a series of nitrogen-doped mesoporous carbons (NMCs) with three-dimensional (3D) interconnected mesopores have been prepared using flour as carbon source, dicyanamide as nitrogen source and colloidal silica as hard template. The optimized material (NMC-4) prepared with the colloidal silica/flour mass ratio of 4 has a high nitrogen doping level of 5.69 at.% and large specific surface area of 995 m(2) g(-1) as well as 3D interconnected mesopores (12.9 nm). As the oxygen reduction reaction (ORR) electrocatalyst among various NMCs, NMC-4 exhibits the superior performance and much better stability and methanol crossover with a four-electron dominant reaction pathway compared to commercial 20 wt% Pt/C. Furthermore, as a supercapacitor (SC) electrode material, NMC-4 exhibits a high specific capacitance of 178.5 F g(-1) at a current density of 0.5 A g(-1) and long cycle life (94.5% capacity retention after 5000 cycles). It also shows a good rate capacity as 76.1% of original specific capacitance remains when the current density increases from 0.5 to 20 A g(-1). The high-performance of NMCs results from the synergetic effects of 3D interconnected mesopores, large surface area, and high N-doping level, enabling fast mass transport and electron transfer during the electrochemical process. This work provides a facile and efficient strategy to heteroatom-doped carbons from extensively available biomass, showing great potentials in electrocatalysis, energy storage, and other applications. (C) 2018 Published by Elsevier Inc

A review of oxygen reduction mechanisms for metal-free carbon-based electrocatalysts

A review of oxygen reduction mechanisms for metal-free carbon-based electrocatalyst

Edge-sited Fe-N-4 atomic species improve oxygen reduction activity via boosting O-2 dissociation

The development of low-cost, efficient, and stable electrocatalysts toward the oxygen reduction reaction (ORR) is urgently demanded for scalable applications in fuel cells or zinc-air batteries (ZABs), but still remains a challenge. Herein, carbon materials with edge-sited Fe-N-4 atomic species (E-FeNC) were synthesized from pyrolysis of abundant Fe-containing biomass using silica spheres as hard template. The E-FeNC delivers remarkable ORB. performance with a half-wave potential of 0.875 V (vs. reversible hydrogen electrode (RHE)), much better than Pt/C (0.859 V), attributed to atomically dispersed Fe-N-4 moieties nearby graphitic edges. The density functional calculations reveal that O-2 molecule adsorbs on Fe-N-4 sites with an energetically favorable side-on configuration with elongated O=O bond rather than end-on form, boosting the subsequent dissociation pathway with a direct 4e reaction route. Using E-FeNC as cathode catalyst, the primary ZAB exhibits high specific capacity of 710 mA h g(-1) and power density of 151.6 mW cm(-2) . The rechargeable ZAB by coupling E-FeNC and NiFe layered double hydroxide (LDH) demonstrates long-term capacity retention over 200 h, superior to that using noble Pt/C and RuO2. This unique carbon material with atomically dispersed metal sites opens up an avenue for the design and engineering of electrocatalysts for energy conversion systems

Nanoheterostructures of Partially Oxidized RuNi Alloy as Bifunctional Electrocatalysts for Overall Water Splitting

Electrocatalytic water splitting, as one of the most promising methods to store renewable energy generated by intermittent sources, such as solar and wind energy, has attracted tremendous attention in recent years. Developing efficient, robust, and green catalysts for the hydrogen and oxygen evolution reactions (HER and OER) is of great interest. This study concerns a facile and green approach for producing RuNi/RuNi oxide nanoheterostructures by controllable partial oxidation of RuNi nanoalloy, which is characterized and confirmed by various techniques, including high-resolution transmission electron microscopy and synchrotron-based X-ray absorption spectroscopy. This nanoheterostructure demonstrates outstanding bifunctional activities for catalyzing the HER and OER with overpotentials that are both among the lowest reported values. In a practical alkali-water-splitting electrolyzer, it also achieves a record-low cell voltage of 1.42 V at 10 mA cm(-2), which is significantly superior to the commercial RuO2//Pt/C couple and other reported bifunctional water-splitting electrocatalysts. Density functional theory calculations are employed to elaborate the effect of Ni incorporation. This simple catalyst preparation approach is expected to be transferrable to other electrocatalytic reactions

Bottom-up evolution of perovskite clusters into high-activity rhodium nanoparticles toward alkaline hydrogen evolution

Self-reconstruction is an efficient method to synthesize active electrocatalysts. Here, the authors demonstrate a bottom-up evolution route of electrochemically reducing Cs3Rh2I9 halide-perovskite clusters to prepare ultrafine Rh nanoparticles with multiply sites for alkaline hydrogen evolution