A sustainable CVD approach for ZrN as potential catalyst for nitrogen reduction reaction

In pursuit of developing alternatives for the highly polluting Haber-Bosch process for ammonia synthesis, the electrocatalytic nitrogen reduction reaction (NRR) on transition metal nitrides such as zirconium mononitride (ZrN) has been identified as potential pathway for ammonia synthesis. In particular, specific facets of ZrN have been theoretically described as a potentially active and selective for the NRR. Major obstacles that need to be overcome include the synthesis of tailored catalyst materials that can activate the inert dinitrogen bond while suppressing the hydrogen evolution reaction (HER) and not being degraded during electrocatalysis. To tackle these challenges, a comprehensive understanding of the influence of the catalyst’s structure, composition, and morphology on the NRR activity is required. This motivates the use of metalorganic chemical vapor deposition (MOCVD) as the materials synthesis route, as it enables catalyst nanoengineering by tailoring the process parameters. Herein, we report the fabrication of oriented and facetted crystalline ZrN thin films employing a single source precursor (SSP) MOCVD approach on silicon and glassy carbon (GC) substrates. First principles density functional theory (DFT) simulations elucidated the preferred decomposition pathway of the SSP, while ab initio molecular dynamics simulations show that ZrN at room temperature undergoes surface oxidation with ambient O2, yielding a Zr-O-N film, which is consistent with compositional analysis from Rutherford backscattering spectrometry (RBS) in combination with nuclear reaction analysis (NRA) and X-ray photoelectron spectroscopy (XPS) depth profiling. Proof-of-principle NRR experiments of ZrN/GC hint towards a possible activity for the electrochemical NRR in sulfuric acid electrolyte.