Comprehensive Study of Structural and Electrocatalytic Properties of Ni–N Thin Films

This work presents a systematic and detailed investigation of the structural, electronic, and electrochemical properties of Ni–N thin films grown using a reactive magnetron sputtering at partial nitrogen flow (RN 2 ) of 0, 15, 50, 75, and 100%. Below RN 2 = 50%, the phase formed is metallic Ni with some N atoms occupying interstitial sites. However, when the RN 2 exceeds 50%, the Ni 3 N phase sets in, and a fully stoichiometric Ni 3 N phase is realized at RN 2 = 100%. As RN 2 increases, the oxidation state of Ni increases and the structural ordering improves, as substantiated by X‐ray absorption fine structure and X‐ray diffraction analysis. Additionally, hard X‐ray photoelectron spectroscopy measurements confirm the formation of a fully stoichiometric Ni 3 N phase at RN 2 = 100%. Finally, the electrocatalytic performance measured through the oxygen evolution reaction clearly demonstrates better performance of Ni 3 N as compared to pure Ni or other Ni–N phases. This work provides essential building blocks to establish Ni 3 N as an environmentally friendly, noble metal‐free, and earth‐abundant catalyst for water splitting reactions.