Study on Nickel Nitride Core Nitrogen Doped Carbon Shell Structure as Electrocatalyst for Oxygen Evolution Reaction
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Date
2023-11
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Addis Ababa University
Abstract
The oxygen evolution reaction (OER) is vital for electrochemical water splitting, enabling a viable, ecologically positive, and sustainable approach for hydrogen energy production. Due to the high costs and restricted availability of noble metal catalysts, transition metal non-oxides such as nitrides, phosphides, selenides, and sulphides present potential alternatives that can give strong OER activity and durability. The OER mechanism is intrinsically sluggish, needing large energy to break hydrogen bonds and produce O-O bonds. Additionally, the high binding energies of critical kinetic intermediates (*O, *OH, and *OOH)—further contribute to the sluggish reaction rates. Nickel nitride (Ni₃N) has gained great attention because of its substantial potential, low cost, and ease of fabrication. Its mechanical stability is strengthened when enclosed in a nitrogen-doped carbon electrocatalyst architecture, Ni₃N@NC; hence, the catalyst can bear the pressures of electrochemical reactions without showing major changes in structure or loss of active sites. The present architecture offers an improvement in charge transfer through void space between a nickel core and a nitrogen-doped carbon shell while introducing additional active sites for catalytic processes. A nitrogen-doped carbon shell with a porous structure facilitates mass transport due to better dispersion of reactants and products. The core-shell samples of Ni₃N@NC were prepared by coating nickel metal with polydopamine using the pH-induced oxidative polymerization in alkaline solution (pH 8.5), then acid etching of the core was performed to introduce a void space between the core and an outer PDA-derived NC shell. In the process, crystalline phases, surface morphologies, microstructures, and composition were characterized using different methods like XRD, FE-SEM, TEM, Raman spectroscopy, and XPS to describe Ni₃N@NC. Accordingly, the electrocatalytic activity of prepared samples was investigated both for OER and hydrogen evolution reactions. It is viewed that the overpotential of the OER electrocatalyst Ni₃N@NC/24hr was 292.8 mV at a current density of 10 mA cm⁻², while the Tafel slope was 110.68 mV dec⁻¹. This further confirmed its catalytic nature towards OER and established its potential in various sustainable hydrogen production applications
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Keywords
water splitting, core shell structure, electrocatalyst, nickel nitride, nitrogen doped carbon, oxygen evolution reaction, hydrogen evolution reaction