Oxygen vacancy-enhanced Ni3FeN/NF nanoparticle catalysts for efficient and stable electrolytic water splitting

The highly effective and economical electrocatalysts hold great importance in the context of water electrolysis. In this work, a nanosheet catalyst (Ni3FeN/NF) composed of nanoparticles for comprehensive water splitting was synthesized through a facile hydrothermal technique followed by a subsequent nitridation process. This catalyst is endowed with an abundance of oxygen vacancies, thereby conferring a richer array of active sites. Therefore, the catalyst demonstrates a markedly low overpotential for the OER of 271 mV at 50 mA cm−2 and an equally low overpotential for the HER of 35 mV at 10 mA cm−2. Serving as a dual-function electrode, this electrocatalyst is employed in overall water splitting in alkaline environments, demonstrating impressive efficiency of 10 mA cm−2 at a cell voltage of 1.45 V. In-situ Raman spectroscopy was employed to elucidate the active phase and dynamic surface structure of the Ni3FeN/NF catalyst by conducting measurements at intervals of 0.1 V. At open circuit voltage (OCV), Ni3FeN/NF exhibited pronounced peaks at 532 and 702 cm−1. Notably, at potentials exceeding 1.40 V, distinct peaks were observed at 473 and 551 cm−1. The manifestation of these dual peaks indicates that γ-Ni(Fe)OOH serves as the predominant active species in the oxygen evolution reaction (OER) mechanism for Ni3FeN/NF.