Mechanistic Insights into the Stabilization of In Situ Formed γ‐NiOOH Species on Ni60Nb40 Nanoglass for Effective Urea Electro‐Oxidation

Abstract

AbstractThe formation of NiOOH on the catalyst surface is widely considered to be the active species in electrochemical urea oxidation reactions (UOR). Though in situ‐formed NiOOH species are reported to be more active than the synthesized ones, the mechanistic study of the actual active species remains a daunting task due to the possibility of different phases and instability of surface‐formed NiOOH. Herein, mechanistic UOR aspects of electrochemically activated metallic Ni60Nb40 Nanoglass showing stability toward the γ‐NiOOH phase are reported, probed via in situ Raman spectroscopy, supported by electron microscopy analysis and X‐ray photoelectron spectroscopy in contrast with the β‐NiOOH formation favored on Ni foil. Detailed mechanistic study further reveals that γ‐NiOOH predominantly follows a direct UOR mechanism while β‐NiOOH favors indirect UOR from time‐dependent Raman study, and electrochemical impedance spectroscopy (EIS) analysis. The Nanoglass has shown outstanding UOR performance with a low Tafel slope of 16 mV dec−1 and stability for prolonged electrolysis (≈38 mA cm−2 for 70 h) that can be attributed to the nanostructured glassy interfaces facilitating more γ‐NiOOH species formation and stabilization on the surface. The present study opens up a new direction for the development of inexpensive Ni‐based UOR catalysts and sheds light on the UOR mechanism.