Conductive Porous Network of Metal-Organic Frameworks Derived Cobalt-Nitrogen-doped Carbon with the Assistance of Carbon Nanohorns as Electrocatalysts for Zinc-Air Batteries

Strong coordination ability of sulfur with cobalt for facilitating scale-up synthesis of Co9S8 encapsulated S, N co-doped carbon as a trifunctional electrocatalyst for oxygen reduction reaction, oxygen and hydrogen evolution reaction

High activity trifunctional non-noble electrocatalysts, targeting oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and oxygen evolution reaction (OER), are rationally designed by integrating the merits of both Co₉S₈ nanoparticles and carbons nanosheets. Herein, Co₉S₈ loaded with S, N co-doped carbon core-shell catalyst (Co₉S₈@SNC) was reasonably designed and synthesized by using the strong coordination effect between Co²⁺ and CS at the molecular level. The significant synergistic effect between the S, N co-doped carbon shell and Co₉S₈ core endows the catalyst with excellent catalytic performance for ORR, HER, and OER reactions. The carbon shell enhances the conductivity of the hybrid material, while the Co₉S₈ core provides the main catalytic active sites. More specifically, the half-wave potential for ORR is 0.846 mV, and the overpotential at 10 mA cm^-2 for OER and HER are 320 mV and 170 mV, respectively. To test its practical application, zinc-air battery assembled by Co₉S₈@SNC shows a high power density of 239 mW cm^-2, excellent rechargeability, and long cyclic stability. This work provides a promising and extensible method to in-situ synthesize core-shell metal sulfides loaded S, N co-doped carbon composites, which can be a promising candidate for electrocatalytic material in energy storage and conversion devices.

Boosting oxygen evolution reaction activity by tailoring MOF-derived hierarchical Co–Ni alloy nanoparticles encapsulated in nitrogen-doped carbon frameworks

The growing demand for sustainable energy has led to in-depth research on hydrogen production from electrolyzed water, where the development of electrocatalysts is a top priority. We here report a controllable strategy for preparing the cobalt–nickel alloy nanoparticles encapsulated in nitrogen-doped porous carbon by annealing a bimetal–organic framework. The delicately tailored hierarchical Co₂Ni@NC nanoparticles effectively realize abundant synergistic active sites and fast mass transfer for the oxygen evolution reaction (OER). Remarkably, the optimized Co₂Ni@NC exhibits a small overpotential of 310 mV to achieve a current density of 10 mA cm⁻² and an excellent long-term stability in alkaline electrolyte. Furthermore, the underlying synergistic effect mechanism of the Co–Ni model has been pioneeringly elucidated by density functional theory calculations.

The hierarchical Co₂Ni@NC nanoparticles realize fast mass transfer for the oxygen evolution reaction (OER). The synergistic effect between Co and Ni can effectively adjust the binding energy tending to an optimal value, further improving the energetics for the OER.

Carbon Nanohorn-Based Electrocatalysts for Energy Conversion

In the context of even more growing energy demands, the investigation of alternative environmentally friendly solutions, like fuel cells, is essential. Given their outstanding properties, carbon nanohorns (CNHs) have come forth as promising electrocatalysts within the nanocarbon family. Carbon nanohorns are conical nanostructures made of sp2 carbon sheets that form aggregated superstructures during their synthesis. They require no metal catalyst during their preparation and they are inexpensively produced in industrial quantities, affording a favorable candidate for electrocatalytic reactions. The aim of this article is to provide a comprehensive overview regarding CNHs in the field of electrocatalysis and especially, in oxygen reduction, methanol oxidation, and hydrogen evolution, as well as oxygen evolution from water splitting, underlining the progress made so far, and pointing out the areas where significant improvement can be achieved.

An Fe-N co-doped tube-in-tube carbon nanostructure used as an efficient catalyst for the electrochemical oxygen reduction reaction

An Fe-N co-doped tube-in-tube carbon nanostructure is synthesized for an efficient oxygen reduction reaction. Thanks to its hollow nature, the mesoporous structure is enriched while defects are not prominent, allowing excellent activity (E _1/2 = 0.851 V) and durability together with methanol tolerance in an electrochemistry test under alkaline conditions. Furthermore, when the material is used as the cathode catalyst of a Zn-air battery, the battery exhibits a peak power density of 181.5 mW cm^-2.