Electrocatalytic splitting of seawater for the production of eco-friendly green hydrogen to serve assorted applications is highly desirable to promote sustainable development globally. Electrodes capable of sustaining strong alkaline conditions while maintaining an industrially desired current density (j) of at least 400 mA/cm² at an appreciably low overpotential of ≤0.6 V and possessing the property of scalability as well as bifunctionality are absolutely necessary for the large-scale rolling out of this electrolyzer technology for commercial implementation. Transition metal nitrides offer higher promises towards the success of this initiative. Herein, we report the synthesis of nanocatalysts (NC-Ni₃Nm/Fe₃Nm) using a polymer (Poly acryloyl hydrazide, PAHz) and transition metals like Ni and Fe. The nanoparticles of Ni and Fe are coated on a FeOOH heterostructure supported on a piece of nickel foam, further, the arrangement is subjected to heat treatment under an N₂ environment to prepare the electrodes. The process offers the possibility of controlling the size of the metal nitride nanoflakes’ during the development of these sustainable electrodes. Since the material preparation procedure is devoid of using any harsh chemicals and reagents hence the procedure can be termed as a green route synthesis. During electrocatalytic activity in the standard 1 molar KOH solution, the working electrode (NC-Ni₃Nm) offers very low overpotential (h) for both OER (0.24V) and HER (0.18V) activity at a j value of 10 mA/cm² supporting bifunctionality. In industrially acceptable electrocatalytic conditions for green hydrogen generation using seawater having 2 molar KOH the overpotential (h) for both OER (0.32V) and HER (0.39V) observed for j₄₀₀ is also quite low hence promising. The electrodes also offer sustainability of over 500 h @ j₄₀₀ in harsh alkaline conditions. It is also worth mentioning that this synthesis procedure can be further extended to prepare similar monometallic and bimetallic nitride electrocatalysts for the purpose of alkaline seawater splitting.

Synthesis of nanocatalyst and development of sustainable electrodes for alkaline seawater splitting

Umaprasana Ojha

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