Metallic Nonstoichiometric Wo3-X Decorated Nife Ldh for Boosted Urea Electro-Oxidation Reaction: The Facilitated Dynamics and Increasing Active Sites

Abstract

Employing urea oxidation reaction (UOR) to aid hydrogen generation from alkaline water electrolysis is an energy-saving and renewable approach compared with traditional energy-intensive anodic oxygen evolution reaction (OER). Undoubtedly, the highly efficient electrocatalyst is the core-section. Herein, a highly efficient UOR catalyst NiFe LDH/WO3-x hybrid, coupling NiFe LDH with nonstoichiometric defective-rich WO3-x is proposed. The introduction of quasi-metallic WO3-x significantly enhanced the conductivity of NiFe LDH and facilitated the electron transfer in the UOR process. More significantly, it modulated the electron structure of active site Ni, promoting the phase transformation from inert Ni2+ to active Ni3+ and concurrently significantly increased surface concentration (ᴦNi) from 1.52×10-4 (NiFe LDH) to 2.45×10-4 (NiFe LDH/WO3-x). Accordingly, the NiFe LDH/WO3-x demonstrated exceptional UOR performance, with a potential of 1.47 V vs. RHE at 50 mA cm-2 and a small Tafel slope of 42.8 mV dec-1, much better than NiFe LDH (57.5 mV dec-1). The urea-assisted water splitting hydrogen generation device also possesses a decreased potential of 80 mV for 50 mA cm-2 compared with pure water electrolysis. This work provides a strategy to improve the electrochemical activities of non-precious metal oxides/hydroxides by coupling conductive metal oxides.

Keywords: NiFe LDH, nonstoichiometric WO3-x, oxygen deficient, electronic interaction, urea oxidation reaction