Modulating Built-In Electric Field Via N-Doped Carbon Dots for Robust Oxygen Evolution at Large Current Density

Constructing a built-in electric field (BIEF) within heterostructures has emerged as a compelling strategy for advancing electrocatalytic oxygen evolution reaction (OER) performance. Herein, the p-n type nanosheet array heterojunction Ni₂P-NCDs-Co(OH)₂-NF are successfully prepared. The variation in interaction affinity between nitrogen within N-doped carbon dots (NCDs) and Ni/Co induces charge redistribution between Co and Ni in the Ni₂P-NCDs-Co(OH)₂-NF-3 heterostructure, thereby enhancing the intensity of the BIEF, facilitating electron transfer, and markedly improving OER activity. The optimized electrocatalyst, Ni₂P-NCDs-Co(OH)₂-NF-3, demonstrates a remarkably low overpotential of 389 mV at 500 mA cm⁻², alongsides a small Tafel slope of 65 mV dec⁻¹, expansive electrochemical active surface area (ECSA), low impedance, outstanding stability exceeding 425 h at 500 mA cm⁻², and a Faradaic efficiency of up to 96%. In situ Raman spectroscopy and density functional theoretical (DFT) calculations elucidate the OER mechanism, revealing that the enhanced BIEF optimizes the adsorption energy of Co³⁺ to OH⁻ and weakened the desorption energy of oxygen during the reaction. The work ponieeringly employed the NCDs as a regulator of the BIEF, effectively tuning field intensity and achieving superior electrocatalytic OER performance under large current density, thus charting new pathways for the development of high-efficiency oxygen evolution electrocatalysts.