Metal–Organic Framework-Derived Hierarchical (Co,Ni)Se₂@NiFe LDH Hollow Nanocages for Enhanced Oxygen Evolution

Abstract

High-efficient electrocatalysts are crucial for fuel cell applications; however, the whole cell performance is generally restricted by the anodic part because of the sluggish kinetics involved in the oxygen evolution reaction (OER) process. Herein, a hierarchical hollow (Co,Ni)­Se2@NiFe layered double hydroxide (LDH) nanocage was synthesized by deriving from the metal–organic framework (MOF) of ZIF-67. Concretely, it involves first fabrication of hollow rhombic (Co,Ni)­Se2 nanocages and then deposition of NiFe LDH nanosheets on the surface of nanocages. Notably, the incorporation of Ni into Co-based ZIF-67 (via ion-exchange) could tail the atomic arrangement of the MOF, exposing more additional active sites in the following selenization treatment. The as-synthesized (Co,Ni)­Se2@NiFe LDH demonstrates splendid OER performance with a small overpotential of 277 mV (to launch a current density of 10 mA cm–2), a small Tafel slope of 75 mV dec–1, and robust durability (a slight stability decay of 5.1% after 17 h of continuous test), not only surpassing the commercial RuO2 but also being comparable/superior to most reported nonprevious metal-based catalysts. Upon analysis, the outstanding OER performance is attributed to the optimized adsorption/desorption nature of iron and nickel/cobalt toward the oxygenated species and partial delocalization of spin status at the interface via the bridging O2–. This work represents a solid step toward exploration of advanced catalysts with deliberate experimental design and/or atom tailoring.

Nitrogen-Doped Carbon-Encased Bimetallic Selenide for High-Performance Water Electrolysis

“…In high-solution Co 2p XPS spectra (Fig. 3b), the Co with different chemical valances could be found, where the Co 3+ 2p 3/2 and Co 3+ 2p 1/2 were located at 777.6 and 792.7 eV, while the location of Co 2+ 2p 3/2 and Co 3+ 2p 1/2 were at 779.5 and 795.8 eV, respectively, in accordance with previously reported penroseit (Co, Ni)Se 2 [2]. In highsolution Ni 2p XPS spectra (Fig.…”

“…Reliable and sustainable supply of clean energy has recently emerged as a critical socioeconomic megatrend [1][2][3][4]. Hydrogen, an ideal carbon-free energy source, with high heat value and environment-friendly characteristics, can be produced by electrochemical water splitting.…”

Engineering Bimetal Synergistic Electrocatalysts Based on Metal–Organic Frameworks for Efficient Oxygen Evolution

“…Interestingly, compared with the Ni 2p 3/2 peak (855.83 eV) of Ni‐MOFs‐i and the Fe 2p 3/2 peak (711.23 eV) of Fe‐MOFs‐i, the peak positions of FN‐2i shift to lower and higher binding energies (Ni 2p 3/2 at 855.51 eV and Fe 2p 3/2 at 711.64 eV), respectively. It suggests that the synergistic effects between two metals occurs when NiFe‐LDH are formed …”

Rapid Fabrication of Ni/NiO@CoFe Layered Double Hydroxide Hierarchical Nanostructures by Femtosecond Laser Ablation and Electrodeposition for Efficient Overall Water Splitting

“…The difference between Co 2p 3/2 and Co 2p 1/2 represents a spin orbital splitting energy of approximately 16 eV, confirming that the Co element was primarily presented as Co 2+ . In addition, the two main peaks of Fe 2p 3/2 and 2p 1/2 were observed at 711.9 and 725.5 eV, respectively, in the XPS peak of Fe 2p (Figure f), corresponding to Fe 3+ . The peaks at 783.3 eV for Co and at 715 eV for Ni were attributed to surface peaks, which originated from the different coordination of the corresponding species …”

“…[32,48] In addition, the two main peaks of Fe 2p 3/2 and 2p 1/2 were observed at 711.9 and 725.5 eV,r espectively,i nt he XPS peak of Fe 2p (Figure 3f), corresponding to Fe 3 + . [49,50] The peaks at 783.3 eV for Co and at 715 eV forN iw ere attributed to surface peaks, which originated from the different coordinationo ft he corresponding species. [51,52] To evaluate the activities towards OER and HER, the prepared samples were investigateda saworking electrode and measured in 1 m KOH solution using at hree-electrode system.…”