Biomass-derived amorphous carbon-modified NiFe-LDH for efficient urea electrooxidation: Electron-deficient Ni3+ sites induced by interfacial electron transfer

Mild hydrothermal strategy well preserves abundant O/N functional groups of Chitosan-derived amorphous carbon. • Chitosan-derived amorphous carbon efficiently stabilizes intrinsic Ni 3+ active sites. • Pre‑stabilized intrinsic Ni 3+ promotes the reconstruction of γ‑NiOOH. • Interfacial electronic modulation lowers UOR overpotential and delivers remarkable UOR activity. Replacing the sluggish oxygen evolution reaction (OER) with the urea oxidation reaction (UOR) offers a promising route for energy-efficient hydrogen production and the electrochemical treatment of urea-containing wastewater. However, the practical application of UOR is still hindered by insufficient anode durability and sluggish UOR kinetics. Herein, biomass chitosan was employed as the carbon precursor to fabricate amorphous carbon-modified coral-like NiFe layered double hydroxide (NiFe-LDH), which was in-situ anchored on nickel foam via a facile one-step hydrothermal strategy. The optimized catalyst achieved remarkable UOR electrocatalysis, requiring only 0.94 V and 0.96 V overpotential to reach 50 mA·cm −2 and 100 mA·cm −2 , respectively, accompanied by a small Tafel slope of 22 mV·dec −1 and outstanding long-term stability exceeding 1000 h at 100 mA·cm −2 . Operando spectroscopic characterizations and density functional theory (DFT) calculations indicated that electron-withdrawing functional groups on chitosan-derived amorphous carbon induced interfacial electron transfer, which stabilized electron-deficient Ni 3+ sites. This pre-stabilized Ni 3+ facilitated the in-situ generation of active γ-NiOOH at low potential, while γ-NiOOH served as the catalytic phase to drive the UOR; the complementary synergy between the two significantly enhanced the overall catalytic performance. This study affords a versatile interfacial modulation protocol for designing high-performance crystalline/amorphous hybrid electrocatalysts, which may offer a promising route for sustainable energy conversion and the electrochemical treatment of urea-containing wastewater. Download: Download high-res image (213KB) Download: Download full-size image Electron-withdrawing O/N groups of chitosan-derived amorphous carbon tunes Ni and Fe 3d- t 2 g orbitals of NiFe-LDH via interfacial charge transfer, stabilizing intrinsic Ni 3+ and reducing UOR overpotential.