With increasing hydrogen demand the ways for carbon-free hydrogen production is sought. In the transition to a net zero emissions energy system, the demand for hydrogen produced from fossil fuels will be replaced by the need for low-emissions hydrogen [1]. In addition, hydrogen energy can be used to generate and store energy and to deal with the intermittent nature of renewable energy sources [2].
A stable and efficient electrocatalyst is required for production of green hydrogen. At this background, transition metal nitrides have raised lots of attention. Their physical properties are similar to those of metallic elements. The inner nitrogens can increase the electron density of d-bands of transition metals, so that the electronic structures of these materials are similar with some precious metals, whose density of states can cross the Fermi level. Therefore, transition metal nitrides have similar conductivities with metals and possess superior electrocatalytic performance. Nanostructured TMNs tend to have relatively large dispersion and more exposed active sites, which have direct improvement for catalytic activity and stability as electrochemical catalysts. [3]. Metallic bonds influence that material have small electrical resistivities and high corrosion resistivity. Covalent bonds influence materials high stress tolerance which gives material high hardness. Ionic bonds points to similar electronic structure to precious metals like Pt and Pd due to contraction of metal d-bands and an expansion of the parent metal lattice [4]. These parameters show high potential for water electrolysis.
The purpose of this work was to synthesize ZrN thin films on AISI 304 type stainless steel, study their structure and electrochemical activity in hydrogen evolution reaction (HER).
Thin films of ZrN were deposited by pulse direct current magnetron sputtering. This method has proved to be fast and efficient way to obtain ZrN coatings of desired thickness of about 250 nm. Coatings were deposited from ZrN target at different conditions by varying the ratio of Ar/N2 in gas atmosphere and applying 200-350 W power. The characterization of prepared electrocatalyst samples was done by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX), Raman spectroscopy, X-ray diffraction spectroscopy, profilometry, and UV-vis spectroscopy. All electrochemical measurements (cyclic voltammetry, chronoamperometry, chronopotentiometry) were performed in 0.1 M KOH electrolyte in a three electrode cell consisting of ZrN/stainless steel substrate as working electrode, Ag,AgCl|KCl(sat) as a reference electrode, and Pt wire as a counter electrode. The experimental results showed that ZrN/stainless steel electrodes are highly stable and active electrocatalysts for hydrogen evolution reaction. Tafel analysis was performed to provide insights into HER mechanism and to evaluate the influence of synthesis conditions on electrocatalytic activity of ZrN thin films.