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The preparation of noble metal‐free catalysts for water splitting is the key to low‐cost, sustainable hydrogen generation. Herein, through a pyrolysis‐oxidation process, we prepared a series of Co‐Fe‐Ni trimetallic oxidized carbon nanocubes (Co1‐XFeXNi‐OCNC) with a continuously changeable Co/Fe ratio (X=0, 0.1, 0.2, 0.5, 0.8, 0.9, 1). The Co1‐XFeXNi‐OCNC shows a volcano‐type oxygen evolution reaction (OER) activity. The optimized Co0.1Fe0.9Ni‐OCNC achieves a low overpotential of 268 mV at 10 mA cm−2 with a very low Tafel slope of 48 mV dec−1 in 1 m KOH. At the same time, the stability of the Co0.1Fe0.9Ni‐OCNC is also outstanding; after 1000 CV cycles, the LSV plot is almost coincident. Moreover, the potential remains almost of the same value at 10 mA cm−2 after 12 h in comparison to the initial value. The excellent electrocatalytic properties can be attributed to the synergistic cooperation between each component. Therefore, the Co0.1Fe0.9Ni‐OCNC is a promising candidate instead of precious metal‐based electrocatalysts for OER. [ABSTRACT FROM AUTHOR]

Hydrogen production is one of the most effective methods for combating the global energy crisis. However, improving the electrochemical performance of oxygen‐evolution catalysts is a significant challenge. In this paper, exceptionally active electrocatalysts for oxygen‐evolution reactions (OERs) were successfully developed and characterized by using SEM, TEM, XRD, BET, and X‐ray photoelectron spectroscopy. The nitrogen‐doped hollow‐carbon‐encapsulated bimetallic nanoparticles (MM′‐NHCNPs) were prepared by using folic acid coordination polymerization. The hollow structure and the synergistic effect of bimetallic doping exhibited remarkable catalytic performance and outstanding stability for the OER in a 1.0 m KOH alkaline electrolyte. For the OER, the overpotential of the best catalyst was only 350 mV at a current density of 10 mA cm−2 with a small Tafel slope of 58 mV dec−1. High durability was also demonstrated by the MM′‐NHCNPs. Such an MM′‐NHCNP catalyst with excellent electrochemical properties provides a promising material for OERs. It′s a wrap! Bimetallic nitrogen‐doped hollow‐carbon‐wrapped nanoparticles (MM′‐NHCNPs) were prepared by using folic acid coordination polymerization. Such an MM′‐NHCNP catalyst with excellent electrochemical properties provides a promising material for oxygen‐evolution reactions (see figure). [ABSTRACT FROM AUTHOR]

Abstract: Metal–organic frameworks (MOFs) and MOF‐derived nanomaterials have recently attracted great interest as highly efficient, non‐noble‐metal catalysts. In particular, two‐dimensional MOF nanosheet materials possess the advantages of both 2D layered nanomaterials and MOFs and are considered to be promising nanomaterials. Herein, we report a facile and scalable in situ hydrothermal synthesis of Co–hypoxanthine (HPA) MOF nanosheets, which were then directly carbonized to prepare uniform Co@N‐Carbon nanosheets for efficient bifunctional electrocatalytic hydrogen‐evolution reactions (HERs) and oxygen‐evolution reactions (OERs). The Co embedded in N‐doped carbon shows excellent and stable catalytic performance for bifunctional electrocatalytic OERs and HERs. For OERs, the overpotential of Co@N‐Carbon at 10 mA cm−2 was 400 mV (vs. reversible hydrogen electrode, RHE). The current density of Co@N‐Carbon reached 100 mA cm−2 at an overpotential of 560 mV, which showed much better performance than RuO2; the largest current density of RuO2 that could be reached was only 44 mA cm−2. The Tafel slope of Co@N‐Carbon was 61 mV dec−1, which is comparable to that of commercial RuO2 (58 mV dec−1). The excellent electrocatalytic properties can be attributed to the nanosheet structure and well‐dispersed carbon‐encapsulated Co, CoN nanoparticles, and N‐dopant sites, which provided high conductivity and a large number of accessible active sites. The results highlight the great potential of utilizing MOF nanosheet materials as promising templates for the preparation of 2D Co@N‐Carbon materials for electrocatalysis and will pave the way to the development of more efficient 2D nanomaterials for various catalytic applications. [ABSTRACT FROM AUTHOR]