Tuning the Activity of Carbon for Electrocatalytic Hydrogen Evolution via an Iridium‐Cobalt Alloy Core Encapsulated in Nitrogen‐Doped Carbon Cages

Abstract

Graphene, a 2D material consisting of a single layer of sp -hybridized carbon, exhibits inert activity as an electrocatalyst, while the incorporation of heteroatoms (such as N) into the framework can tune its electronic properties. Because of the different electronegativity between N and C atoms, electrons will transfer from C to N in N-doped graphene nanosheets, changing inert C atoms adjacent to the N-dopants into active sites. Notwithstanding the achieved progress, its intrinsic activity in acidic media is still far from Pt/C. Here, a facile annealing strategy is adopted for Ir-doped metal-organic frameworks to synthesize IrCo nanoalloys encapsulated in N-doped graphene layers. The highly active electrocatalyst, with remarkably reduced Ir loading (1.56 wt%), achieves an ultralow Tafel slope of 23 mV dec and an overpotential of only 24 mV at a current density of 10 mA cm in 0.5 m sulfuric acid solution. Such superior performance is even superior to the noble-metal catalyst Pt. Surface structural and computational studies reveal that the superior behavior originates from the decreased ΔG for HER induced by the electrons transferred from the alloy core to the graphene layers, which is beneficial for enhancing CH binding.

Oxygen/Fluorine Dual‐Doped Porous Carbon Nanopolyhedra Enabled Ultrafast and Highly Stable Potassium Storage

“…More importantly, the density of edge plane defects has a considerable correlation with the electron‐transfer activation . In other words, a larger I D1 / I G intensity ratio indicates a significant improvement of D 1 band derived form a vibration mode of carbon atoms activated by edge plane defects, which leads to a faster electron transfer rate and extra potassium‐ion storage sites . As shown in Figure b, the I D1 / I G of OFPCN is larger than that of ZrO 2 /C, indicating that more defect sites were introduced after the oxygen/fluorine heteroatom doping in the OFPCN electrode.…”

“…The G band corresponds to the E 2g vibration mode of the defect‐free sp 2 carbon structures, while the D 1 band is related to the A 1g symmetric vibration mode of graphitic domains activated by edge plane defects due to heteroatom doping . The D 3 band is assigned to amorphous carbon and the D 4 band is associated with the presence of polyene‐like species or ionic impurities . More importantly, the density of edge plane defects has a considerable correlation with the electron‐transfer activation .…”

Fabrication of N, P-Codoped Mo2C/Carbon Nanofibers Via Electrospinning as Electrocatalyst for Hydrogen Evolution Reaction

“…1,2 At present, most of the hydrogen produced by reforming methane steam and coal gasification, which were not only energy consuming but also environment destruction. 3,4 In recent years, there has been an increasing interest in electrocatalysts for hydrogen evolution reaction (HER) for water splitting due to simpleness, efficiency and the high-purity hydrogen production. Generally, platinum (Pt)-based transition metal as the state-of-the-art catalysts for HER hinders large-scale application because of the high price, exiguity, and easy to poison.…”

Sub‐Nanometer‐Sized Iridium Species Decorated on Mesoporous Co3O4 for Electrocatalytic Oxygen Evolution

“…In order to identify the surface chemical composition and valence state information of the Ir−Co 3 O 4 heterostructure, X‐ray photoelectron spectroscopy (XPS) is conducted. The high‐resolution Ir 4 f XPS spectra of Ir−Co 3 O 4 (Figure a) can be splitted into four peaks at 60.9, 62.4, 63.8, and 65.5 eV, corresponding to the binding energies of Ir 0 4f 7/2 , Ir 4+ 4f 7/2 , Ir 0 4f 5/2 , and Ir 4+ 4f 5/2 , respectively, indicating that the Ir element on Ir−Co 3 O 4 samples mainly exists as oxidation state . The high‐resolution Co 2p XPS spectra of Ir−Co 3 O 4 (Figure b) exhibits two main peaks located at the binding energies around 779.6 and 794.6 eV are attributed to the characteristic peaks of Co 2p 3/2 and Co 2p 1/2 orbit levels, respectively …”