Tuning the Activity and Stability of CoCr-LDH by Forming a Heterostructure on Surface-Oxidized Nickel Foam for Enhanced Water-Splitting Performance

Abstract

The development of low-cost, efficient catalysts for electrocatalytic water splitting to generate green hydrogen is a hot topic among researchers. Herein, we have developed a highly efficient heterostructure of CoCr-LDH on NiO on nickel foam (NF) for the first time. The preparation strategy follows the simple annealing of a cleaned NF without using any Ni salt precursor, followed by the growth of CoCr-LDH nanosheets over the surface-oxidized NF. The CoCr-LDH/NiO/NF catalyst shows excellent electrocatalytic activity and stability toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in a 1 M KOH solution. For OER, only 253 mV and for HER, only 185 mV overpotentials are required to attain a 50 mA cm −2 current density. Also, the long-term stability of both the OER and HER for 60 h proves its robustness. The turnover frequency value for the OER increased 1.85 times after the heterostructure formation compared to bare CoCr-LDH. The calculated Faradaic efficiency values of 97.4 and 94.75% for the OER and HER revealed the high intrinsic activity of the heterostructure. Moreover, the heterostructure only needs 1.57 V of cell voltage when acting as both the anode and the cathode to achieve a 10 mA cm −2 current density. The long-term stability of 60 h for the total water-splitting process proves its excellent performance. Several systematic pre-and post-experiment characterizations prove its durable nature. These excellent OER and HER activities and stabilities are attributed to the surface-modified electronic structure and thin nanosheet-like surface morphology of the heterostructure. The thin, wide, and modified surface of the catalyst facilitates the diffusion of ions (reactants) and gas molecules (products) at the electrode/electrolyte interface. Furthermore, electron transfer from n-type CoCr-LDH to p-type NiO results in enhanced electronic conductivity. This study demonstates the effective design of a selfsupported heterostructure with minimal synthetic steps to generate a bifunctional electrocatalyst for water splitting, contributing to the greater cause of green hydrogen economy.

Metalation-Induced Triazine-Based Covalent Organic Framework as a High Performance Electrocatalyst for Oxygen and Hydrogen Evolution Reactions

“…Undeniably, understanding the structural alterations occurring during the intricate oxygen evolution reaction (OER) process is crucial . To unravel this, the electrode material subjected to the CA study was scrutinized through X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HR-TEM) analysis.…”

Designing a Phenalenyl-Based Dinuclear Ni(II) Complex: An Electrocatalyst with Two Single Ni Sites for the Oxygen Evolution Reaction (OER)

“…These measured currents at 1.02 V were plotted against the scan rates, and the specific capacitance on an anodic sweep was calculated through the slope of the graph (Figure S16b). Considering the value for the specific capacitance of a flat surface as ∼40 μF cm –2 of the real surface area, , the electrochemically active surface area (ECSA) of the GC-1 was measured to be 3 cm ECSA 2 . The mass activity of the catalyst was measured to be 14.2 mA mg –1 at 1.53 V, by measuring the estimated mass of complex 1 (0.05 mg) deposited at the electrode’s surface (Figure S16d).…”

“…The faradaic efficiency for the OER catalyzed by GC-1 was calculated to be 86%. Further, the reaction kinetics at GC-1 is analyzed through the Tafel plot obtained via the chronoamperometry technique . A potential required to achieve a current density of 10 mA cm –2 was applied for 100 s to achieve a constant current value.…”

“…The applied potential was iR corrected and plotted against the log of current density ( J ), log| J (mA cm –2 )| in Figure c. Using the Tafel equation, η = a + b log­( j ), where η defines the overpotential, b denotes the Tafel slope, and j is the current density, the Tafel slope was obtained from Figure c . Interestingly, a very low Tafel slope, 40 mV dec –1 , revealed the fast OER kinetics by complex 1 .…”

Iron Integration in Nickel Hydroxide Matrix vs Surface for Oxygen-Evolution Reaction: Where the Nernst Equation Does Not Work

“…The SEM image exhibits a certain roughness indicative of a textured topography. This roughened surface could potentially contribute to a larger surface area, which might enhance the material’s catalytic properties or adsorption capabilities. − …”