Transition metal nitrides (TMN) have gained increasing attention as active materials for numerous energy related applications including catalysis and energy storage due to their unique properties. The metal nitrogen bonding in TMN consists of covalent, ionic and metallic bonds which influence the material characteristics. While the metallic bonds lead to small electrical resistivities and high corrosion resistance, the covalent bonding enhances stress tolerance, accompanied by high hardness and brittleness. Furthermore, the ionic bonding leads to comparable electronic structure to that of precious metals such as Pd and Pt due to a contraction of the metal dbands and an expansion of the parent metal lattice. Among the numerous TMN's, ZrN has been recently identified as a promising material for a range of possible applications that include plasmonic devices, catalyst for oxygen reduction reaction (ORR) and the nitrogen reduction reaction (NRR). Although ZrN displays favourable electrochemical activity to ORR and NRR while being cheap and abundant compared to commonly employed noble metals, in the bulk form conventionally used, there are a limited number of active sites which significantly reduces the efficiency and hinders its implementation in practical catalytic applications. The (100) facets of rock-salt structured ZrN, in addition to other TMNs such as CrN, NbN, and VN were theoretically described as possibly active and selective for the NRR and stable under typical electrocatalytic potentials. The experimental evaluation of these computational descriptions is currently lacking, mainly due to difficulties in preparing facet controlled TMNs. Therefore, tailoring the catalysts surface morphology towards high efficiency on large scale is crucial for implementation of ZrN in practical catalysis. These challenges motivate the use of chemical vapor deposition (CVD) as the method of choice for ZrN deposition since it allows precise tuning of the surface features as well as the composition of the material, by variation of the process parameters including the precursor, temperature, and pressure. In addition, CVD is industry compatible because it enables a scalability of catalyst production towards high volume. Early CVD approaches towards zirconium nitrides mostly employed ZrCl4 in combination with a mixture of N2 and H2 at temperatures above 1000 °C13,14 or NH3 in a temperature range from 750 °C to 1400 °C. However, the high deposition temperatures made it difficult to apply the grown zirconium nitrides in microelectronics, radiological coatings and optics. In addition, the likelihood of halide contamination of the thin films, which are known to degrade the mechanical properties of the material, necessitated the need for alternative precursor chemistries that enable moderate process conditions, while being halide free. Hence, metal organic chemical vapor deposition (MOCVD) approaches were developed that employed all-nitrogen coordinated amide complexes namely, tetrakis(dimethylamino)zirconium [Zr(NMe2)4], tetrakis(diethylamio)zirconium [Zr(NEt2)] and tetrakis(ethylmethylamio)zirconium [Zr(NEtMe)4] as precursors for ZrN either via single source precursor (SSP) approaches or in the presence of H2 and N2 or NH3. To enhance the limited thermal stability of the aforementioned parent amide complexes, a mixed amide and guanidinate precursor, namely [Zr{η 2 -(iPrN)2CNMe2}2(NMe2)2] i.e. [Zr(guan)2(NMe2)2] (1) was developed and successfully employed in proof-of-principle SSP MOCVD of ZrN at moderate process conditions. In this study, we take advantage of these promising results and optimize the MOCVD process to deposit a ZrN NRR catalyst employing ammonia-free process conditions. Avoiding NH3 in nitride fabrication allows for a simplified process optimization and delivers further benefits with regard to reduced toxicity, environmental pollution, greenhouse gas emissions (resulting from NH3 production), and safety concerns. For NRR applications, the crystal orientation of the material plays a crucial role, because theoretical investigations suggest that the rock-salt structured (100) facets of ZrN lead to enhanced catalyst stability during catalysis. Furthermore, N vacancies are considered as the active surface sites for the nitrogen activation in the NRR in the Mars-van Krevelen mechanism. Thus, controlling the number of N-vacancies as well as tuning their activity by introducing heteroatoms to vary the lattice properties is considered a viable approach to enhance the catalytic properties of the material. Interestingly, although numerous theoretical studies propose ZrN as a promising material for the NRR, to the best of our knowledge, there is only one study that conducted experimental investigations of this material. Hanifpour et al. tested the NRR activity of ZrN thin films grown by DC magnetron sputtering on Si(100) substrates that indicate catalytic activity for NRR, using linear sweep voltammetry in Ar vs. N2 media. However, the ammonia concentration produced in isotope labelled NRR experiments (which is required to prove genuine NRR activity) was below their detection limit, leaving the proof of genuine NRR activity open. In addition, the ZrN catalyst consisted of not only the energetically favourable rock salt (100) facets, but also other higher energy facets such as (111), ( ) and (311). This result and the potential of ZrN as catalyst for NRR motivates us to conduct a systematic optimization of the ZrN MOCVD process parameters including the deposition temperature, precursor flow and the deposition pressure to obtain ZrN films with a preferential orientation along the (100) plane. In the present study, we successfully deposited oriented ZrN layers with facetted grains along the (100) plane that is proposed as active for electrocatalytic NRR. Since the actual NRR experiments are conducted on glassy carbon (GC) substrates, the growth characteristics of the MOCVD process were investigated on both Si(100) and GC substrates. To investigate the decomposition pathway of the employed SSP (1) to ZrN at elevated temperatures, fragments detected in electron impact mass spectrometry (EI-MS) were used to predict possible reaction pathways. Those pathways were correlated with density functional theory (DFT) calculations to understand preferred SSP reactions. To correlate the catalyst properties with NRR activity, investigation of the structure, composition and surface features were conducted by complementary characterization methods. X-ray diffraction (XRD) and Raman spectroscopy gave insight into the structure while the composition was investigated by Rutherford backscattering spectrometry in combination with nuclear reaction analysis (RBS/NRA), depth profiling X-ray photoelectron spectroscopy (XPS) and further DFT studies of surface oxidation. The surface features were investigated by scanning electron microscopy (SEM) and bright-field transmission electron microscopy (BF-TEM) was employed to investigate the shape of the crystal grains. Additionally, the Zr and N distribution in the film was investigated by scanning transmission electron microscopy coupled with energydispersive X-ray spectroscopy (STEM-EDS) while selected crystal domains were analysed by selected area electron diffraction (SAED). Furthermore, the optical properties of the thin films grown on quartz glass were investigated by UV-Vis spectroscopy. Proof of principle NRR experiments of the ZrN thin films grown at optimized condition were performed in 0.1 M sulfuric acid electrolyte. Increased currents in N2-saturated electrolyte compared to background experiments in Ar-saturated electrolyte suggest some activity towards the NRR and provide an encouraging foundation for in depth catalytic studies of ZrN NRR in future.