Ultrafine Bimetallic Nickel–Cobalt Alloy from a Layered Hydroxide for Oxygen Evolution Reaction and Capacitors

Abstract

NiCo bimetallic alloys on layer double hydroxide-derived nitrogen-doped carbon support (NiCo@LDH-NC) were derived from bimetallic NiCo-layered double hydroxides (NiCo@LDH). With the structural and compositional advantages, NiCo@LDH-NC exhibits an XRD pattern of NiCo alloy particles supported by X-ray absorption spectroscopy (XAS) analysis, high-resolution transmission electronic microscopy (HR-TEM) imaging, and HR-TEM lattice spacing analysis, which confirms the NiCo alloy particle with coherent substitution of Co strongly aligned with the (111) plane of Ni particles. This resulted in a strained lattice of the NiCo alloy (fcc) with strong interaction between pure Ni and Co metals. The relation of the host Ni (fcc) lattice with dopant Co in NiCo@LDH-NC exhibits a free atom-like electronic structure as compared to host Ni. In the oxygen evolution reaction (OER) of water electrolysis, the monolayer electrode of NiCo@LDH-NC exhibits minimum overpotentials of 330 and 346 mV at 10 and 20 mA cm–2, respectively, with an improved electrokinetics-driven 36.4 mV dec–1 Tafel slope obtained from the Tafel plot. The charge transfer resistance (R ct) value obtained for NiCo@LDH-NC was 2.48 Ω, confirming a faster charge transfer kinetics throughout the electrode-electrolyte interface that influenced the OER activity. This investigation on the NiCo alloy and associated electronics is promising for upgrading the features of the bimetallic alloy nanoarchitecture and their potential for advanced electrochemical processes.

Convenient Synthesis of NiCo Alloy Nanoparticles Encapsulated by N-Doped Porous Carbon for the Oxygen Evolution Reaction

“…The XRD pattern of the Ni@NC electrode material shows distinct diffraction peaks at 44.5, 51.6, and 76.3°, which could be indexed successfully to the (111), (200), and (220), respectively, which matched standard cards for the Ni fcc structure (JCPDS 04–0850) . When Co ions are added, the peak of the sample is obviously shifted to a lower angle, between the peak positions of Ni and Co (JCPDS 15–0806) metals. , The three peaks belonging to the NiCo alloy phase are located at 44.3, 51.6, and 76.1° corresponding to the (111), (200), and (220) planes, respectively . This indicates the successful synthesis of NiCo alloy .…”

“…17 When Co ions are added, the peak of the sample is obviously shifted to a lower angle, between the peak positions of Ni and Co (JCPDS 15−0806) metals. 18,19 The three peaks belonging to the NiCo alloy phase are located at 44.3, 51.6, and 76.1°c orresponding to the (111), (200), and (220) planes, respectively. 18 This indicates the successful synthesis of NiCo alloy.…”