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

Abstract 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 Ni 2 P‐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 Ni 2 P‐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, Ni 2 P‐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 Co 3+ 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.