Ni Nanoparticles on Ni Core/N-Doped Carbon Shell Heterostructures for Electrocatalytic Oxygen Evolution

Abstract

Supported Ni-based nanocatalysts have attracted much attention to replace noble metal catalysts (e.g., IrO2) for the oxygen evolution reaction (OER) due to their low costs. However, their low activity is the main hindrance for their use in the practical OER application. In this study, a Ni-based core–shell material (Ni@Ni-NC) is produced through the heat treatment of a mixture of urea and NiCl2·(H2O)6. Multiple analysis data reveal that the Ni@Ni-NC consists of a Ni nanoparticle core and several tens of nanometer-thick, N-doped carbon (NC) shell materials, in which atomically attached Ni-based species were homogeneously distributed. Ni@Ni-NC exhibits excellent electrocatalytic OER performance with over- and onset potentials of 371 mV and 1.51 V, respectively, which are better than those of commercial IrO2. As control samples, structural and electrochemical properties of various composites (Ni nanoparticles + N-doped graphene, Ni nanoparticles + C3N4, atomically dispersed Ni on a C3N4 surface) and acid-treated Ni@Ni-NC are investigated. These experiments reveal that the well-dispersed Ni–NC species and core–shell structures play pivotal roles in improving the electrocatalytic OER performance. Furthermore, density functional theory (DFT) calculations suggest the dual-site OER mechanism of the Ni–NC active species with a significantly low reaction barrier. The mechanisms for the formation of core–shell structures are studied with control samples, which are produced from different heating times, and DFT calculation suggested that the core/shell structure formation is attributed to the cohesive energy of the Ni particles and strong bonds between the Ni and NC supports. This work provides a facile strategy for designing supported Ni catalysts with core–shell architecture for electrocatalytic reactions and other advanced applications.

N-Doped Graphene Supported Cu Single Atoms: Highly Efficient Recyclable Catalyst for Enhanced C–N Coupling Reactions

“…Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) images of Cu SACs/NG (Figure a,b) demonstrated that the wrinkled structure was well maintained in comparison with the pristine graphene shown in Figure S1 (see Supporting Information, SI), and an absence of visible particles could be observed. The lattice fringe is measured to be ∼0.34 nm from the wrinkles in the HRTEM image (Figure b), which is in good agreement with the (002) crystalline plane of graphene . The selected area electron diffraction (SAED) pattern (inset in Figure b) revealed two concentric rings with diffraction radii of ∼0.34 nm and ∼0.20 nm corresponding to the (002) and (101) planes of graphene, respectively .…”

“…The lattice fringe is measured to be ∼0.34 nm from the wrinkles in the HRTEM image (Figure 3b), which is in good agreement with the (002) crystalline plane of graphene. 38 The selected area electron diffraction (SAED) pattern (inset in Figure 3b) revealed two concentric rings with diffraction radii of ∼0.34 nm and ∼0.20 nm corresponding to the (002) and (101) planes of graphene, respectively. 39 The well concentric rings confirmed the presence of graphene without any highly crystallized phases of Cu catalysts.…”

Predominant Catalytic Performance of Nickel Nanoparticles Embedded into Nitrogen-Doped Carbon Quantum Dot-Based Nanosheets for the Nitroreduction of Halogenated Nitrobenzene

“…As shown in Figure b, the N 1s XPS spectrum of NCQDs-500 is well divided into two peaks at 398.6 and 400.4 eV corresponding to pyridinic-N and pyrrolic-N, respectively . However, the N 1s XPS spectrum of Ni@NCQDs-500, as shown in Figure c, is divided into four peaks at 398.08, 398.88, 399.78, and 401.08 eV corresponding to pyridinic-N, N–Ni, pyrrolic-N, and graphitic-N, respectively; ,− the atomic content of nitrogen by XPS element analysis was found to be 5.46%. The existence of N–Ni with a binding energy similar to that of pyridinic-N also proves that Ni species have interacted with N species on the surface of NCQDs.…”

Advances in Electrospun Materials and Methods for Li-Ion Batteries

“…The performance of the charge cycle and the discharge were consistently attributed to the substantial lithium storage capacity of the electro-spun composite. The fibers also have a good rating capacity, and the electrical impedance also diminishes as the number of cycles climbs [ 118 , 119 , 120 ].…”